Metra GMOS-01 Wiring Interface

Connect a new car stereo and retain OnStar®, factory door chimes, and audible safety warnings in select GM vehicles

Item #: 120GMOS01

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113 Reviews

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Metra's GMOS-01 interface lets you replace the factory radio in select OnStar-equipped 2000-up GM vehicles using the existing wiring and connectors. Even if you don't subscribe to OnStar, you'll need this interface to connect an aftermarket stereo.

Hook the GMOS-01 to your aftermarket radio, mount the module, and plug it into the existing factory plug. Get the great sound you want, and keep all important safety features intact. And you can adjust volume settings for OnStar as well as the safety chimes. Also, once you turn off the ignition in these GM vehicles, the radio continues to play until you open the door. This interface maintains that function with your new aftermarket radio.

This interface is compatible with select 2000-up GM vehicles. If you haven't done so already, please enter your vehicle information or call an Advisor at 1-888-955-6000 to find out if this item is compatible with your vehicle. Warranty: 1 year.

Note: The GMOS-01 will not work with factory-installed Bose car audio systems.

Note: Most vehicles will require additional installation parts — please identify your vehicle if you haven’t done so, then check here for a list of parts. You can also call an Advisor for more information.

Hands-on research

What's in the box?

Download owner's manual

  • GMOS-01 Class II Data Bus interface
  • Wiring harness with 10-pin Molex on one end and bare wires on the other
  • Wiring Harness with 12-pin Molex on one end and 24-pin Molex and 12-pin Molex on the other (plus bare wires)
  • Installation instructions

Product Research


Overview: The GMOS-01 lets you install an aftermarket receiver in select late model GM vehicles without losing the OnStar Emergency Services features or the chime that warns the door is open. Please check the Crutchfield Vehicle Selector to confirm compatibility with your vehicle.

Note: This adapter is not compatible with factory Bose or Monsoon systems.

Connections: The module includes a 10-pin harness (5 pins used) that connects to the switched power and front speaker leads of the new radio. A second harness (12-pin, 10 used) connects the module to the factory OnStar and radio plugs, plus the rest of the wiring for the new radio.

OEM Steering Wheel Control Compatible (optional): The GMOS-01 features a right-angle 3.5mm connector that lets you keep your GM vehicle's OEM steering wheel controls via the optional Axxess Steering Wheel Control Interface (120ASWC1, sold separately).

Volume: The volume is adjustable for both the OnStar output and the warning chime.

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team. They verify what’s in the box, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.

Metra GMOS-01 Wiring Interface Reviews

Average Customer Review:

113 reviews
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Worked really well

Written By Brian WV, West Virginia on Sunday, March 29, 2015

Works so well on my h3 its awesome to have the correct wiring the first time with security it will be correct with home installs the first timer can use this product with ease! kept my onstar and hands free calling also

Pros: great ,comes with option wiring for steering wheel controls ans onstar is retained!

Cons: non

Does not Work

Written By George, SA, Texas on Friday, March 27, 2015

Trying a simple Kenwood double din install in a 2005 Tahoe. I found the wiring instructions for the GMOS unit very simple, matched up well with both aftermarket radio and factory plug. However after 2 weeks of calls and emails traded with Metra tech support the unit will still not initialize. No chimes, no 12V to radio, nothing.

Pros: Straight foreword install. Tech support is available and responsive

Cons: Doesn't work

Harness for Chevy Trailblazer

Written By Jake, Arizona on Monday, March 23, 2015

Crutchfield Customer Review (What's this?)

So far the product has worked really well. I bought this to install an aftermarket cd player/tuner in a Chevy Trailblazer. Most of the wiring was pretty strait forward. The wire colors matched up pretty well with the wires from the new unit, except there were 2 red wires. Instructions were vague on this installation, however after a little research online the 2 red wires were suppose to be connected to the red constant power wire for the unit. Other than that everything else was a breeze.

Pros: For the most part pretty strait forward with connecting wires by color.

Cons: Picture wiring diagrams would help.

Works Great

Written By CME, Michigan on Thursday, March 05, 2015

Crutchfield Customer Review (What's this?)

Works great. It's a little intimidating at first sight but follow the directions and go one wire at a time.

Pros: Works great

Cons: looks intimidating


Written By Devon, Anchorage, AK on Sunday, February 15, 2015

Crutchfield Customer Review (What's this?)

Great product, quick and easy to install. Had it wired and ready to go within 10 minutes.

Pros: Quick, easy, all the wires are labelled.

Cons: None

Metra GMOS-01 Wiring Interface

Written By Anonymous, west haven ct on Sunday, February 15, 2015

Crutchfield Customer Review (What's this?)

Bought this product for my 05 Saturn Relay with on star. Replace factory radio with an aftermarket radio. Hooked up all the necessary wires & plugged into original harness in car. No problems with it so far.

Great product

Written By Mb, New York on Monday, February 09, 2015

Crutchfield Customer Review (What's this?)

I had this installed in my 2005 GMC Envoy and it was an easy install. All the wiring matched perfect so it took half the time it normally would. Great product

Pros: Easy to install.

Cons: None

Bad instructions

Written By Michael, Boston on Wednesday, January 07, 2015

Crutchfield Customer Review (What's this?)

If only the instructions gave a complete guide of how to complete, then the product would be good

Crutchfield response on Monday, January 12, 2015 We forwarded this review to our Technical Support team for follow-up. Lifetime tech support comes with every Crutchfield purchase.

What was this for?

Written By mmaxon888, Fort Calhoun, NE on Wednesday, October 15, 2014

Crutchfield Customer Review (What's this?)

Not even sure what this adapter was supposed to do. I was under the impression I would retain my steering wheel controls, but that is not the case. Doesn't look like I needed this part at all.

Pros: Easy to attach. Had question during install, Crutchfield customer service answered phone right away and fixed my issue. Knew exactly what I needed to plug in even though I didn't know exactly what I was asking for!

Cons: Did not do what I thought it would. In fact, it doesn't look like I needed the adapter at all.

Crutchfield response on Tuesday, October 21, 2014 Our Tech Support team helped clarify why the customer needed the GMOS-01 and helped him get the other feature he wanted (to retain his steering wheel controls) by adding the ASWC-1 adapter. The customer reports that he is completely happy with his new gear and found our service to be very helpful.

Metra GMOS-01 Wiring Interface

Written By DennisK, Mendon, MA on Sunday, October 12, 2014

Crutchfield Customer Review (What's this?)

Not for the faint of heart. I am an electronics technician and I needed to call Crutchfield for assistance. Instructions are not great. These are one size fits many and there is no guidance as to what to do with the extra wires. Don't hesitate to call for assistance.

Pros: It works.

Cons: Poor instructions.

Works as advertised

Written By Tom N., Dillsburg PA on Tuesday, September 02, 2014

Crutchfield Customer Review (What's this?)

I'm not sure what everyone complained about in these product reviews. I thought the instructions were easy to understand and that the product works as advertised. I read the instructions 1-2 times and then hooked it up to my new stereo step by step. I'll admit that upon first glance wiring this to the stereo can be daunting, but hooking every wire step by step turned out to be very simple

Pros: Everything that this is supposed to do (Bluetooth, OnStar) works

Cons: None


Written By jim, Portsmouth, Va on Thursday, August 28, 2014

Crutchfield Customer Review (What's this?)

very easy to install and a great time saver

Cons: none

Metra GMOS-01 Wiring Interface

Written By Anonymous, Bedford, OH on Tuesday, August 19, 2014

Crutchfield Customer Review (What's this?)

Does what it says keep all factor options

metra gmos 01 factory intigration adapter

Written By cris f., hamilton,oh on Monday, June 23, 2014

Tricky but read it carefully all detailed well.

Pros: If u know what u r doing it's easy as 123!

Cons: None

Metra GMOS-01 Factory Integration Adapter

Written By Tim, Aurora, CO on Friday, June 20, 2014

Crutchfield Customer Review (What's this?)

I soldered all the wires so the went well

Pros: For my application it worked great.

Cons: Some of the wires could be longer to make connections easier.

Metra GMOS-01 Factory Integration Adapter

Written By MikeO, Denver, CO on Sunday, May 18, 2014

Crutchfield Customer Review (What's this?)

Having to buy this otherwise Crutchfield won't support your service was a bit of a drag. But, after installing this I'm glad I put it in to retain the original chimes and OnStar.

Pros: Keeps the door chimes and OnStar. Easy to install.

Cons: Necessary purchase if Crutchfield support is desired.

Metra GMOS-01 Wiring Interface

Written By Anonymous, Cumming, GA on Wednesday, April 30, 2014

Crutchfield Customer Review (What's this?)

Hookup was quite simple; however, I had to google to determine the exact location for some of the wires. The instructions could be a little more clear and could have mentioned that there are two red wires but only one is necessary. Crutchfield didn't recommend the Steering Wheel Remote module as a needed accessory. It is mentioned in the details of the unit but not when you select the headunit. Only this and the mounting adapter came up as a needed accessories.

Pros: Works perfectly.

Cons: Had to research for details on some of the instructions as not all wires are mentioned in the instructions.

OnStar interface

Written By Tom J, Newington, CT on Sunday, April 06, 2014

Crutchfield Customer Review (What's this?)

I still do not have an AM antenna working

Pros: Works for interface

Cons: Incomplete instructions, can't get AM radio antenna to work.

Good harness

Written By Zeke, Sun Prairie, WI on Friday, April 04, 2014

Crutchfield Customer Review (What's this?)

This was the same harness that I had bought before from a certain electronics store but was charged about double there and it was even an return but anyways the harness is good and works great one thing was that I had a lot of extra wires that we're not needed for my stereo

works great

Written By Julzee, Pittsburgh PA on Monday, March 31, 2014

Crutchfield Customer Review (What's this?)

I really like the lower volume of the door and seat belt chimes. I don't always wear my seat belt and the intermittent 'nagging' always got on my nerves but not any more...:)

Pros: nice soft chime vs original louder nagging

Cons: none

Great product

Written By Anonymous, lagrange ky on Saturday, March 15, 2014

Crutchfield Customer Review (What's this?)

I had to buy thus adapter to install my Pioneer head unit because I have Onstar on my Chevy Trailblazer. Everything works great! Chimes even sound factory & not corney like some do! Once I got my old reciever out the adapter was very easy to install!

Pros: Factory sounding chimes Clear sound Easy install

Cons: A little more pricey than I wanted

Metra GMOS-01 Wiring Interface

Written By 2007trailblzr, Yadkinville, NC on Monday, March 10, 2014

Crutchfield Customer Review (What's this?)

A must have when doing an install on a trailblazer it simplifies the process.

Pros: Makes the install almost seamless. Retains the onstar feature as well as the factory chimes.

Cons: No way to really control the volume of the chimes they are too loud.

Take your time and this will work.

Written By RSS, Benton.Ar on Monday, February 17, 2014

The product works well but the instruction manual isn't very clear. The manual doesn't give clear instructions on connecting the GMOS box , infact part of my manual was missing. With help from the Crutchfield tech (theses guys ROCK!) support I was able to complete the installation. Just be sure that all wires that are not used are taped up well and make contact with nothing or you will be replacing fuses. Found this out the hard way when some tape slipped off.

Pros: Works well and maintained all the safety features of my truck.

Cons: Instruction manual can get vague in some places. Pages were missing.

Does what it says

Written By Chris M, Collegeville, PA on Thursday, February 06, 2014

Crutchfield Customer Review (What's this?)

Vehicle: 2006 Pontiac Grand Prix GT with factory radio (without Monsoon). Gear: Pioneer FH-X700bt, ASWC, GMOS-01

I will start by saying I have never installed a head unit before in my life. This was my first install. When you look at the GMOS-1, you might get intimidated by the mess of wires included with the Adapter. Don't be. As long as you are not color blind, installation is incredibly simple. The instructions are pretty easy to read too. I don't understand why people think they are confusing. I'll repeat, I have never installed a radio in my life. In fact this was the first time I have picked up a soldering iron. Trust me, if you have ANY cognitive skill at all, the directions are easy to follow.

Functionality is dead on as described by the product. I LOVE that I can adjust the volume of the chime. Although I do hate the chime, I did not want to lose them. I am extremely happy that I can put the volume as low as I want.

Integration with the ASWC interface is prety awesome. Again, those instructions are pretty simple to to follow as well. My steering wheel controls work flawlessly and I am very happy that I did not have to splice into the factory female harness. The GMOS-01 makes installing the ASWC even easier than it already is.

Just get the dang GMOS and stop being cheap.

Pros: Chimes work (play through driver front speaker only) Adjustable chime volume RAP retained On Star retained ( I don't use it) ASWC integration NOTE: A lot of people are confused as to why there are two red (ignition) wires on the 16 pin harness of the GMOS-01. It is there in case you are using the ASWC. Connect one to your HU harness (doesn't matter which). Then connect the ASWC's harness red wire to other red wire in the 16 pin harness. Tape/cap it off if not using, duh.

Cons: Mess of wires, but common sense should tell you how to organize them for an easier install in the dash. Electrical tape or zip ties are your friends to group wires effeciently. Obviously, solder and heat shrink connections. Never seal an electrical connection with tape.

Metra GMOS-01 Wiring Interface

Written By John O, Houston TX on Friday, January 10, 2014

Crutchfield Customer Review (What's this?)

I would like to start off by saying everything is setup and working great. Second, This harness is a universal setup for ALLLLot of vehicle models for alllll the different stereos so it scared me at first. I took the harness over to my uncles (ocd/electrical engineer). Yes he got it installed/wired/working. As everyone has stated the instructions borderline a writing nightmare. If you lay out the harnesses and get pigtail connectors on your stero harness you can easily get the harness hooked up fast. Yes there is about 9 wires I didnt use and to the OCD person it makes you double check everything. The system works great and retains all factory chimes and do-dads. 2006 base model envoy with pioneer deck.

Pros: It works

Cons: Have an extra 20 for the installer ready or buy them lunch

Metra GMOS-01 Wiring Interface

Written By kyle, monroe Tennessee on Sunday, January 05, 2014

Crutchfield Customer Review (What's this?)

Product was alittle intimidating at first due to the many wires. But with the help of directions included and the wires being color coordinated installation was easy.

Pros: Great directions and friendly customer service that was extremely helpful and knowledgeable

Cons: Two wires were not red like my factory car wiring harness but were pink instead. But they did have the correct writing on them which helped out.

Confusing, but works

Written By BobF, New Orleans on Sunday, December 15, 2013

Lots of extra wires, instructions not very detailed. After I hooked up the radio I had a problem with the sound, but after a couple of calls to tech. support everything is working fine. The reason I buy from Crutchfield is there customer service and tech support.

I've seen better

Written By ZeeB, Manchester, NH on Thursday, December 12, 2013

Crutchfield Customer Review (What's this?)

The instructions are really quite thin, I had a bunch of extra wires left over at the end of putting this together. I ended up calling Crutchfield tech to sort things out.

Keeping the Chimes alive

Written By Chris, Olathe, KS on Friday, November 22, 2013

Crutchfield Customer Review (What's this?)

Very simple and straight forward to install. Wire diagrams and color coding made this a snap.

Pros: Keeps my factor chime intact.

Cons: Additional install.

Does the job!

Written By DJ, Columbia, SC on Tuesday, October 01, 2013

Crutchfield Customer Review (What's this?)

All the alarms and sounds were retained. That's what it is supposed to do.

Pros: Works well.

Cons: none

Great Product

Written By DarrenG, Nebraska on Tuesday, October 01, 2013

Crutchfield Customer Review (What's this?)

Easy install, works as advertised.

Pros: Adjustable chime volume.

Cons: None

Works as promised.

Written By Bob W, Shrewsbury, MA on Tuesday, October 01, 2013

Crutchfield Customer Review (What's this?)

Bought this to maintain my OnStar and factory chimes... Works perfect! Lots of wires including some extra that weren't needed for my install, but I figured it out by searching forums online.

Pros: Works well. Shuts off stereo for OnStar voice and turns it back on when OnStar is done.

Cons: OnStar voice only comes through front left speaker. Pricey (even with half off for buying a head unit at the same time) Wiring diagram could be more helpful.

Review for the Metra GMOS-01

Written By Rich, Somers, NY on Tuesday, September 24, 2013

Crutchfield Customer Review (What's this?)

Works as advertised. Haven't missed a beat with OnStar and door chimes. Wiring diagram was a little confusing, but Crutchfield tech support answered all of my questions.

Pros: No problems and works as advertised.

Cons: Wiring diagram

You get what you pay for

Written By Josh, Michigan on Saturday, August 31, 2013

I purchased this with a new pionner double din with the mixtrax,knowing little for what it was for.I've installed many decks and never had to use something like this.FIRST, theres alot of wires you wont use if you dont have a monsoon system or steering wheel controls.SECOND, theres two red power wires you have to twist together and connect to red power wire on deck,witch should have come pre-done or at least saying something about it the directions.THIRD,I dont like how chimes only come from drivers speaker,at first i thought i had it wired wrong but its normal i suppose.And the thing wont store my date and time on the dash anymore.Did Everything by the directions and even called Crutchfield for help,OVERALL this product works(sort of) but not in anyway near factory condition.Not happy with it.On a side note,Crutchfield's customer support is awesome,never been on hold more than 2 minutes and those guys really know what there doing. A+ to you guys in tech.As for you guys in the product buying department,you need to sit down with Metra and get these things fixed because even for the price,its not worth it.

Pros: dont really have one,just needed it

Cons: pain in the butt to install,low quality

Great for price.

Written By Joeh24, Dallas tx on Monday, August 12, 2013

Crutchfield Customer Review (What's this?)

For the price it's a great deal. 50% off with buying stereo.

Pros: Chimes volume adjustment,on star adjustment.

Cons: None

First one died secound one worked...

Written By Dave C, Currituck, NC on Friday, August 02, 2013

Crutchfield Customer Review (What's this?)

First time installer. I was a little confused with all the wires but I'm a technical person and had no problem figuring it out. The first unit work until I put everything back in and then the deck wouldn't come back on. It was just a Pioneer DEH-X5500HD, nothing special. So, I ran a double fuse wire to the deck and it worked. Then the battery started dieing so I asked around and no one could help. Then I called Crutchfield and they said it might be the brain. So, they sent me a new adapter and that one worked. I the problem is fixed and no more dead batteries. The only reason I gave this four stars and not five is because the first one died after I did all that work.

Pros: It's worked

Cons: First one worked then died

Worked for awhile

Written By Tim, PortOrchard , WA on Wednesday, July 24, 2013

What they don't tell you; Chimes come from left front speaker only, low fuel chime is gone, and radio won't dim with lights on. Worked as I described, and learned to live with these faults. Now the deck goes into "protect" mode when I turn left randomly. Had the deck out numerous times and nothing is loose. popped the cover off the module, nothing appears loose. All connections are soldered and shrink wrapped. I have installed numerous decks over the years, so I am no new to this. I agree with the other review, wiring diagram is horrible. Not happy at all!

Pros: none

Cons: see review

Top Notch Product

Written By Phil, Fresno, CA on Tuesday, July 09, 2013

Crutchfield Customer Review (What's this?)

Adapter works very well with new receiver and factory equipment.

Pros: Good price, with receiver purchase.

Cons: None


Written By Jeff, Houston,TX on Monday, July 08, 2013

Crutchfield Customer Review (What's this?)

Installed in an 06 Suburban and hooked up to a JVC KD-A845BT alongside the Axxess ASWC-1. Everything works as advertised. I soldered and shrink wrapped all connections for a nice clean install. The completed harness was a mess with 2 interface boxes and multiple pig tails, but it all works.

Pros: Price, ease of install

GMOS-01 Unreliable

Written By kn, Atlantic. City on Sunday, July 07, 2013

Crutchfield Customer Review (What's this?)

Installed in my 2008 Grand Prix with a Kenwood navigation receiver, worked great for a few months. Then one night the receiver would not turn on. I removed the Kenwood and sent it for repair. Reinstalled the repaired Kenwood and it worked. This problem happened again in a few months, Kenwood was again repaired and reinstalled successfully. Next time this problem recurred, I unplugged everything then reinstalled: Kenwood worked without being repaired. Then it happened again. This time I simply unplugged the GMOS-01 connector then replugged it, and the Kenwood worked again! The problem was not the Kenwood receiver, but the intermittent faults in the GMOS-01.

Pros: Perform as described when it works

Cons: Unreliable. Keep shutting down the receiver randomly, requiring unplugging the GMOS.

GMOS-01 Factory Integration Adapter

Written By JBroc, Philadelphia, PA on Wednesday, June 12, 2013

Crutchfield Customer Review (What's this?)

used in a 2007 Hummer H3, I had someone installed, but i called around for prices for this part. and Crutchfield beat it by $50.00! Just what I needed... and the price was GREAT!


Written By Anonymous, petersburg va on Tuesday, June 11, 2013

Crutchfield Customer Review (What's this?)

I install my self is easy

GMOS-01 adapter cable

Written By Tom, Albuquerque, NM on Thursday, May 09, 2013

Crutchfield Customer Review (What's this?)

Bought this to use with my new JVC KD-R740BT in my 2005 Chevy Tahoe. I am an electronic tech so all of the soldering of wires from the new deck cable to the adapter cable went well. Great instructions. Lots of extra bundles of cables to stuff back up into cavities.

Pros: All safety chimes work well. Crutchfield cuts price in half when you buy a deck from them at the same time. Nice deal but still darned expensive for an adapter cable with a small electronic interface box.

Cons: Not all connections were shown in drawing. Had some left over connectors but must not need them because everything is working fine. I would like to know what some of those extras are for. Cost is high.


Written By Paul, Brandon, MS on Monday, April 29, 2013

Crutchfield Customer Review (What's this?)

Worked as needed

GMOS-01 wiring harness

Written By Clint, Santa Fe, NM on Saturday, April 27, 2013

Crutchfield Customer Review (What's this?)

Fairly simple to install. One 45 second call to Crutchfield had all unused wires noted and the installation simplified.

Pros: Easy to install.

Cons: Instructions are almost perfect.

Does what it's suppose to

Written By Lab4, Wyoming on Thursday, April 18, 2013

Crutchfield Customer Review (What's this?)

Works like a charm for my '05 Colorado, but creates a mess of a wire harness when you get everything together. I am a bit OCD about trying to keep a clean look for all the wiring I do whether its car audio or home entertainment. it might all be hidden, but a clean install is easier to work on or add to. Even after I took some extra time trying to clean this thing up it still ends up looking like a knot of wire. I know that it is hidden, but it makes it hard to work on things under the dash. The instructions also do not cover the 3.5 male connector that is on one branch of this thing or the second lead on 16pin harness that goes with the new deck harness, but after a call to tech support with this question, which seemed to be a common one they get, I just taped the 3.5 branch outta the way and connected the extra lead together with the other 2.

Pros: Works easy install, as long as you follow the instructions.

Cons: it is a mess of wires

technology is a wonderful thing

Written By Benjamin, Cleveland Ohio on Sunday, April 07, 2013

Crutchfield Customer Review (What's this?)

Using Crutchfield outfit my car app made finding the right part the first time so easy and hassle free. Once I received the part installing the part was not difficult at all. In fact the instruction sheet was barely read. Thanks Crutchfield.

Pros: Very very very easy to understand and install.

Cons: Taking it out of the package was a little rough. My blade wasn't sharp enough. Lol.


Written By Javier, Yuma, Az on Thursday, March 28, 2013

Crutchfield Customer Review (What's this?)

Easy Instructions easy to use

Pros: Simple and easy love it

Ok Stuff

Written By BrianD, St. Clairsville, OH on Friday, March 08, 2013

Crutchfield Customer Review (What's this?)

Not really sure about this one. The adapter is required for my car, 2004 Grand Prix, to still have door chimes.

Pros: Keeps my door chimes working. Assembled on workbench

Cons: Was not an easy install. Kind of confusing, but it is possible to figure out.

2011 Colorado crew can

Written By Kory, Louisiana on Monday, March 04, 2013

Crutchfield Customer Review (What's this?)

Works great. All factory safety alerts work and sound just like factory. Very easy to wire up.

Pros: You can do all wiring on work bench then plug in the pig tales to factory harness.

GM Chimes Adaptor

Written By Bill L, Texas on Tuesday, February 26, 2013

Crutchfield Customer Review (What's this?)

This device works as advertised. Connections are a lot more difficult as compared to previous Crutchfield hook ups. I had to make 13 solder connections and blank off numerous wires.

Thanks to Crutchfield's tech assistance it was manageable.

Pros: Works well Crutchfield tech support.

Cons: Lots of connections and little instructions.

Worked Perfectly!!

Written By Al B., Florence, SC on Saturday, February 23, 2013

Crutchfield Customer Review (What's this?)

This adapter was easy to install with perfect instructions for my vehicle and all factory chimes and OnStar worked flawlessly with my new Pioneer FXH-700BT stereo.

Pros: Ease of installation

Works great!

Written By Tibor, CA on Monday, January 14, 2013

Crutchfield Customer Review (What's this?)

Works as it is supposed to.

Metra GMOS-01 installed in 2004 Envoy XUV

Written By Stan, Atlanta, GA on Thursday, January 03, 2013

Crutchfield Customer Review (What's this?)

Worked as designed. I selected this unit as I don't have steering wheel controls. Crutchfield adviser pointed me in the right direction to make the proper choice. I installed it in three steps. Matched wires to radio harness and twisted together. Soldered all wires and wrapped with electrical tape. Then neatened up the complete package with tie wraps. Installed in the Envoy with the Radio. Verified everything worked before putting dash and center console back together. One problem is that I should have adjusted the tone volume higher. I didn't take into account the higher radio volume once I started using it. I am an Electronics / computer geek, so I was able to read and understand the instructions / wiring diagram. Would be a little complicated for a person without some technical knowledge and should be left to a pro. The installation is only two weeks old.

Pros: Works as advertised. All functions work.

Cons: Comes with two red wires and had to call Crutchfield to get clarification. Turns out you can use either wire. This isn't in the manual / wiring diagram

Metra GMOS-01 Wiring Interface

Written By Anonymous, joliet, IL on Wednesday, January 02, 2013

Crutchfield Customer Review (What's this?)

works fine and has pretty good instructions for installation.

Cons: for a first time car stereo installer, the instructions left too many things out. I ended up with multiple wires and plugs I wasn't sure what to do with that were left out of the instructions. All I had to do was tape them off and not use them but it still caused some confusion.

GMOS adapter

Written By Allan, Florida on Wednesday, December 26, 2012

i rated this adapter so low because the NASA engineers wouldn't be able to decipher the wiring instructions.

Pros: it works

Cons: wiring instructions the worst i have ever seen

Does the job

Written By Kevin F, Woburn, MA on Wednesday, December 12, 2012

The unit does what it is supposed to do. The door chimes, etc. all still work, as does the speaker. One small minus was that there were two different orange with white strip wires, I connected to the one described in the documentation, and the radio does not automatically dim at night. Don't know if would have worked with the other wire.

Pros: Keeps all of the integrated functions working.

Cons: Either the directions or my reading of them didn't work for dimming illumination.

Crutchfield response on Tuesday, December 18, 2012 We forwarded this review to our Technical Support team for follow-up. Lifetime tech support comes with every Crutchfield purchase.

Works like a charm

Written By Neal S, Suffolk, VA on Saturday, August 18, 2012

This thing works great. Installed in 03 Avalanche. Ill admit its overpriced and that the instructions are a bit lacking. It already has the wiring for steering wheel controls, all you need is the module, but you have to buy that package separately, or wait till the all-in-one set is in stock at Crutchfield, so you end up with an extra harness you dont use. I did use all the wires attaching to the head unit unlike other reviewers that didnt use them all. I was able to install it without any problems, or phone calls to tech support, and Im a long way from a pro stereo installer. Hopefully it will play well with the other kids, (in motion video bypass and wireless back-up camera when they show up in a few days) it is a lot to try to stuff back into the dash but eventually it fit. Thanks Crutchfield for the great customer service before the sale!

Pros: It works like it is supposed to!!

Cons: overpriced, although I got it for half price buying the Pioneer AVH 2400 BT

more than enough

Written By David s, Elko, NV on Tuesday, August 07, 2012

Crutchfield Customer Review (What's this?)

Product works as described, however. If you are not savvy at 12v electrical systems and this is your first stereo you will be lost. there are three parts of this harness, it is not plug and play, there is an optional harness that is not detachable so you have a dozen left over wires including a 12v hot wire that will be floating around under the dash sparking and shorting out all kinds of stuff if you do not secure it properly, not in the instructions, all in all it does what it is supposed to. amatures- get help!!!!

Pros: works as it is supposed to.

Cons: confusing, made for more options and non removable third part of not needed harness

Functions as Described

Written By CC, North Carolina on Saturday, July 14, 2012

Crutchfield Customer Review (What's this?)

I wish I could have bypassed using this thing. I spent more time on figuring this out than I did the rest of my install. Instructions are somewhat vague. Took 3 calls to Crutchfield support to get things figured out but they were awesome and had the answers I needed right away. Each call only took about 5 minutes with no hold time. Props to the support team!!! Also, I did have to wire in a seperate speaker to hear my chimes. I simply used an old PC speaker I found laying around my workshop and it did the job. Unit has a very cheesy way of setting the Onstar volume control by actually shorting a wire to ground to get the setting you want.

Pros: Does what it's supposed to do.

Cons: Seems expensive even at half price. Instructions were vague.

GM Adaptor / OnStar

Written By Mark, Birmingham, AL on Friday, June 29, 2012

Crutchfield Customer Review (What's this?)

Excellent piece of equipment. Very intimidating at first glance. Lot of wires, Lots of wires. Tech department offered some very patient and timely advice. Works perfectly but for a small glitch with the Onstar system. The reciever should mute when Onstar comes on. It does not. I must turn the reciever sound down to hear and talk with Onstar. Could be the install but the wires were specifically labled. No big deal.

GM Factory Integration Adapter

Written By Mark G, NY on Sunday, June 17, 2012

Crutchfield Customer Review (What's this?)

I did not like this product. I could not figure out how to install it and did not use it.

Overpriced Installation Accessory

Written By ElvinK, East Bank,WV on Sunday, June 03, 2012

Crutchfield Customer Review (What's this?)

Car manufacturs have ripped us off on the requirements to replace a factory radio. Plus the aftermarket manufactures have come in like vultures to price gouge. There is absolutely no reason why it should cost this much for this adapter (even at half price it is a little steep for no more than what it is). Plus it is not very reliable. For some reason, I have to unplug my connectors at the box and reconnect them to get it to work again. Does this randomly and cant figure it out.

Pros: Connects to factory wiring. Eases radio install.

Cons: Expensive. Unreliable.

Crutchfield response on Wednesday, June 06, 2012 We forwarded this review to our Technical Support team for follow-up. Lifetime tech support comes with every Crutchfield purchase.

2002 Trailblazer

Written By Dennis, New Jersey on Sunday, May 27, 2012

Crutchfield Customer Review (What's this?)

Great product, looks more complicated then it is. Installed in my 2002 Trailblazer and it did exactly what it was suppose to do.

Poor instructions but great service!

Written By Ben, Raleigh, NC on Saturday, May 05, 2012

Crutchfield Customer Review (What's this?)

Product works great. Instructions were pretty bad, and I had to call customer service twice to find out what to do with wires that were not addressed by the instructions. Customer Service was terrific and walked me through the wiring. Worked perfectly when I plugged it into the stereo.

Pros: Works Great. Great customer Service

Cons: Bad instructions

Works well in my Colorado

Written By Bill, Jamestown, NY on Monday, April 02, 2012

Crutchfield Customer Review (What's this?)

This should be free with the GM installation kit. The instructions were too technical, I ended up matching the colors of my GM harness and stereo then looking to see what was left. If you don't read the instructions, you could end up leaving a couple wires intact that you need to cut. At the end of the day - it worked, but its nothing to get excited about and is too expensive for what it is.

Pros: Keep your chimes and On Star

Cons: Expensive Poor instructions Extra wires left over that you don't use - the instructions don't tell you what they are for and that they may not be used Requires you to have a little more than common sense to hook up

A must have for applicable vehicles

Written By defkon77, norton, ohio on Monday, April 02, 2012

Crutchfield Customer Review (What's this?)

I work on GM cars and understand how important this item is for A/M head units.....this installed easy,kept my vehicle like factory(retains RAP,uses door speaker chime, kept OnStar working like factory)....just before i bought this item I bought one from another retailer for twice the price( uses its on speaker and did not keep OnStar) was $90!!!...I returned it and bought this item instead

Pros: retains factory functions.....this imporant for safety and for any installer that cares about not being a "hack" when installing radios.

Cons: NONE!!!!


Written By AznHammer, Winston Salem NC on Saturday, March 03, 2012

Crutchfield Customer Review (What's this?)

Work great, and good price with for the on-star integration. It sucks that GM requires it, but the product works fine.

As far as actual issues below talking about pops/chimes not working correctly, I wonder how much of that is an install problem. All my chimes are working as expected.

Pros: Cheapest one I've seen with on-star

Cons: I don't care of the new door chime sound.

Metra GMOS-01 Wiring Interface

Written By capnrobi, Tampa FL on Sunday, February 12, 2012

Crutchfield Customer Review (What's this?)

I wonder if it was really necessary. My truck never had OnStar

Mostly works

Written By AB, Rocky Mount, NC on Saturday, February 04, 2012

Crutchfield Customer Review (What's this?)

Installed in a 2008 Colorado and although most chimes work the way they used to, not all work.

Pros: Easy to install.

Cons: Not all chimes work correctly.

A necessary evil

Written By Anonymous, Greenville SC on Tuesday, January 31, 2012

Crutchfield Customer Review (What's this?)

I hated the thought of spending the extra hundred bucks for this product, but the 50% off with head unit purchase made it palatable. Product works as described when installed properly. Do the splicing work on the bench, rather than in-car. Then, it's just plug-n-play when you go to mount it in the vehicle. The instruction set is minimal but it has all the necessary information.

Pros: Works as described.

Cons: Expensive but necessary.


Written By j g, ft riley ks on Tuesday, January 24, 2012

Crutchfield Customer Review (What's this?)

great price, need to have product

Metra GMOS-01 Wiring Interface

Written By ToddG, Potterville, MI on Thursday, January 19, 2012

Crutchfield Customer Review (What's this?)

This item had one glaring problem when used with a 2008 Pontiac Grand Prix: The GMOS-1 would cause the driver's door speaker to make a loud, electrical 'pop' sound everytime you inserted the key into the ignition... or, if the key was in the ignition and you opened the door. It had to do with the GMOS-1 "Chime" function. I switched to the GM VT_GMRC-O1 instead, which has it's own built in 'factory style' chime speaker and then it worked flawlessly. I recommend using the GMRC-01 for this year/make of car. I did not have the Monsoon factory radio setup.... just the standard, run of the mill factory radio which I replaced with a JVC KWHDR720.

Pros: Everything worked great.... EXCEPT.... THE CHIME FUNCTION CREATED A STATIC/POP sound when key was inserted into ignition.

Major Headache

Written By Anonymous, Oklahoma City, OK on Saturday, December 17, 2011

Crutchfield Customer Review (What's this?)

1. Comes prewired with an additional connector and 3.5mm plug that the directions/pictures don't even address.

2. Lots of wires (not a big deal), throw in less than stellar directions, and you're left wondering.

3. Installation was pretty straight forward, thought I was good to go, worked perfect, until I came out to a dead battery the next day. Traced the problem to this unit feeding constant 12V power to the ACC wire. So the radio was always on. Yes, I double checked my wiring and everything was done according to the directions. The radio receives constant 12V direct from factor harness, but relies on the GMOS01 for the ACC 12V, so the problems was defiantly the unit.

Don't Over Think It

Written By ag, Charleston, SC on Sunday, November 27, 2011

Crutchfield Customer Review (What's this?)

If a colorblind 22 year old can figure it out working out of the back of his SUV, at night, under a street light, anyone can. Yeah, it's a lot of wires and different colors, but if you match up exactly as the directions say and ignore the wires you don't use, you should be fine.

Pros: works well

Cons: a little confusing

Metra GMOS-01 Wiring Interface

Written By chasjake, Cortland, Ohio on Thursday, October 06, 2011

Crutchfield Customer Review (What's this?)

Used this on a new stereo install in a 2011 Colorado. It works well. The wiring directions / diagram are a little tough to follow but I made it through. The chime is a little more sterile sounding that the factory chimes but who really cares.

Unorganized and Bulky!

Written By JasonK, Kankakee, IL on Thursday, October 06, 2011

Crutchfield Customer Review (What's this?)

This thing is the most unorganized wiring harness I've ever seen!

I took it out of the box and read the instructions for about 45 minutes trying to figure out where the extra black 12pin connector plugged into and the 3.5mm Male. Finally had to call Crutchfield and apparently its for a steering wheel control that's NOT EVEN MENTIONED ONCE in the instructions!

Not to mention this thing is HUGE and I have a mid-size truck. Try fitting that in the dash!

Just as advertised

Written By Johnson, Charleston,. SC on Tuesday, August 30, 2011

Crutchfield Customer Review (What's this?)

Pay attention to the directions and you'll be fine. Lots of wires, but easy to bundle together once all are connected. Made all the connections at the dining room table prior to installation and everything worked as described. Made the after market radio a seamless transition. Didn't need the On Star or amplifier options, so can't comment on them.

Directions are Confusing

Written By JackR, Pittsburgh, PA on Saturday, August 06, 2011

Crutchfield Customer Review (What's this?)

READ INSTRUCTIONS CAREFULLY!!! They are very confusing, color codes on wiring are duplicated, and some additional explanation would have been helpful. Had to call Crutchfield twice to get it all figured out. Also the unit is quite big and you will need to find a location to put the box so it does not interfer with the radio and wiring. There has to be a simpler way to retain the factory chimes, but after all that, it does work well.


Written By Cory, Eugene, OR on Monday, July 18, 2011

Crutchfield Customer Review (What's this?)

works as advertised, maintains all factory features in my 2007 Grand Prix

ok but not great.

Written By ivanE, Grand Rapids, MI on Saturday, July 02, 2011

my stereo stays on untill i open the door, the chime work but you must have the aftermarket unit on if you remove the stereos faceplate it will no longer work. when hitting the onstar button the music won't go mute, thats something the factory unit used to do. I have installed a scosche one in a monte carlo 2001 and the chime works even if you remove the stereos face plate.

Metra GMOS-01 Wiring Interface

Written By Anonymous, TAMPA FL. on Thursday, June 09, 2011

Crutchfield Customer Review (What's this?)


2007 TrailBlazer w/o OnStar

Written By stress, Pittsburgh, PA on Monday, June 06, 2011

Crutchfield Customer Review (What's this?)

The device does exactly what it was designed to do. The installation was easy, even for someone who never messes with vehicle electronics. Don't forget that you'll need to buy some wire connectors and electrical tape! As for the tone, it honestly sounds just like the GM tone from the 80's. It's truly nothing bad -- and very easy to get used to.

OnStar adapter

Written By Donnie, Vineland, NJ on Tuesday, April 19, 2011

Crutchfield Customer Review (What's this?)

Dont let all the wires scare you. It is & was a very easy install. At least on my
Envoy it was. Tone takes a little getting used to, but not anoying

Overpriced But Works Flawless

Written By Sundown, Upstate, NY on Monday, March 28, 2011

Crutchfield Customer Review (What's this?)

Wiring was extremely simple and took little to no time other then soldering. Once wired up, just plug it into the radio and factory harness and you are good to go. Still have OnStar, door chimes, and seatbelt chimes. Back up, park/parking brake and vehicle speed sensor are a big plus for installing a DVD, navigation or backup camera. I will say this item is EXTREMELY overpriced (half this price would be much more reasonable but thats what Crutchfield charges with a receiver purchase anways) and the quality is just good not great but it serves its purpose and works flawless. Review is based on a 2008 Hummer H3.

Like a SNAP!

Written By Brian, Virginia on Sunday, March 27, 2011

Crutchfield Customer Review (What's this?)

Been some years since I changed an aftermarket stereo. I was going to pay and
have it done for me, but a co-worker suggested Crutchfield. Not only did they walk
me through what I needed, but the installation of this item was easier than you
could imagine. Nowadays with electronics and the conglomeration of wires - IT
CAN GET DISCOURAGING. It came with detailed instructions with the product and
from Crutchfield - It was a piece of cake!

Better than the old ones

Written By txplshrk, Corpus Christi TX on Monday, March 14, 2011

Crutchfield Customer Review (What's this?)

This one works a lot better than the old adapters. I had one just like this
that sounded horrible, ever since they changed the design on this it seems to
work better. Wiring connections are spot on and easy to follow. Be careful on
how high you turn up the volume knob on this thing! Man it gets really loud.

work well

Written By hope, chicago on Thursday, February 24, 2011

Crutchfield Customer Review (What's this?)

this unit work well. was very easy to install and i have no problem with it

It's like I never switched out my old OEM stereo

Written By EvansB, Arizona on Thursday, February 24, 2011

Crutchfield Customer Review (What's this?)

Bought this bad boy and was able to still hear my On Star and my Seat Beat/Door
Open chimes. All I had to do was follow the instructions to turn up the volume
on the OnStar audio.

Metra GMOS-01 Wiring Interface

Written By Robert P, Phoenix, AZ on Sunday, February 06, 2011

Crutchfield Customer Review (What's this?)

I used this kit to install a Clarion CD Receiver that I removed from another
car. I am glad I saved the original wiring instructions from Crutchfield from
the first installation. Soldering together all the wires was very time
consuming but the wiring diagrams were easy to follow. I was amazed that red
wire connected to red and blue to blue.....All the wire colors from the old
Clarion matched this new kit. After installation, all chimes and warnings work
just fine. I usually don't have this much luck on the first try.

Super Easy Install and Great Instructions

Written By Deb, Hillsborough, NC on Monday, January 31, 2011

Crutchfield Customer Review (What's this?)

The kit made the install really easy with detailed instructions. My dad is an electrician and
watched me install. The instructions even addressed the function of the wires that are not
used so when he asked me why I didn't use them I could point out they were for the back
speakers we didn't have or if the radio had nav built in.

What a piece of junk!

Written By Dirk C, Ellendale, ND on Saturday, October 09, 2010

Some of the wires had to be added on to, some of the wires were mismarked on the wires compared to what the documentation said. The documentation was contradictory. And worst of all, it just doesn't work. It doesn't chime, it cuts out the left speakers when error messages flash across the dashboard. The speed sensitive volume control doesn't work as advertised.

Metra GMOS-01 Wiring Interface

Written By Derrick T, Fairview Heights, Il on Thursday, September 30, 2010

Crutchfield Customer Review (What's this?)

I believe this module is really over priced and the instructions could be more detailed, but if you take your time, the average person can hook this module up. The main reason I purchased this module was to keep the warning chimes. Prior to installation in the dash, I turned the volume screw clockwise and counter clockwise and I still have not heard a chime yet. Other than that I guess it does what it suppose to do. After soldering all of those connections, I refuse to cut the wires and return it because of the warning chimes and waiting a week to 10 days for a replacement. Since I only paid half price and I was told this was not an optional part I guess I would recommend this to a friend but I would check it out complete before making all the final connections