Metra GMOS-04 Wiring Interface

Connect a new car stereo and retain OnStar®, the audible safety warnings and chimes, and the Bose® audio system in select GM vehicles

Item #: 120GMOS04

In Stock

211 Reviews

Your price: $84.99 Earn up to 85 Rewards points

Add to Cart

+ Add to wishlist + Email me alerts for this product

View all associated offers

Does it fit my car?

Select your car

Find what fits your car

Metra's GMOS-04 GM radio replacement 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 adapter to connect an aftermarket stereo.

Once you connect your in-dash receiver to the interface, you'll get the great sound you want, and keep these important features intact. The Bose amplified speakers and the OnStar system will operate with your new radio, as well as the door chime and audible safety warnings. This interface gives you convenient plug-in connections for the Axxess steering wheel control adapter (not included) that works with most aftermarket stereos – that means less wiring work for you.

Also, once you turn off the ignition in these GM vehicles, the factory 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-and up GMC, Chevrolet, Oldsmobile, Cadillac, Pontiac, Isuzu, and Hummer vehicles. Warranty: 1 year.

Important Note: 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 your GM vehicle's warning chimes are integrated with the factory radio. If so, certain warning chimes in your vehicle may be disabled by installation of an aftermarket receiver. You must use the recommended Crutchfield interface to retain the warning chimes. Failure to do so may result in serious injury or death.

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

Metra GMOS-04 Wiring Interface Reviews

Average Customer Review:

211 reviews
Review this product
Great Gear Giveaway

Submit a review and then enter to win a $350 rewards card


Review this product:

Thanks for taking the time to share your experiences about this product. Please be sure to focus your comments on the product itself. Read our Review Guidelines for more information.

Your email won't be visible. Please use the email address that is associated with your order.
(e.g., JohnD) Your review will be signed using the display name and location
(e.g., Charlottesville, VA)

Click on a star to rate the overall product on a scale of 1-5
1500 characters left
  Attach a YouTube Review
Crutchfield Video Review Guidelines
  • Only submit videos that you made or are authorized to use.
  • Do not submit videos that contain music, video or visuals that are copyrighted and belong to someone else.
  • Please see our Review Guidelines for more information.
500 characters left
500 characters left

Does what it's supposed to do.

Written By kerk, Minnesota on Monday, October 26, 2015

Crutchfield Customer Review (What's this?)

We don't ever really use OnStar, but it also manages other beeps toots whistles and dings, so I guess I needed it.

Fairly Easy

Written By Aaron L, Tennessee on Sunday, September 27, 2015

Crutchfield Customer Review (What's this?)

Fairly easy to wire up and install. Also got the steering wheel adapter. The instructions for the two were a little muddy because the came separately, but some parts were duplicates. Would be much better if these could be purchased together as a kit instead of buying separate pieces. Took about an hour and a half to prewire everything to get ready to install. Followed install directions, and the unit worked seamlessly with my new radio. Only had to adjust volume slightly to get it where I wanted it.

Pros: Fairly straightforward to install

Cons: Wish it was bundled with steering wheel adapter in same box


Written By Linda, Washington on Tuesday, September 22, 2015

Crutchfield Customer Review (What's this?)

After 2 days of scratching our heads on why this was not working correctly, we discovered that the 18 pin connector was not seating correctly into the box (this caused the stereo to turn off and on intermittently). We had to remove and unplug the stereo again and reseat the wires in the box. Problem solved. Wasted a lot of time and mind matter over this one. Have to say Crutchfield has awesome customer service. Tech support was great.

Pros: Now that it is working it seems to be good (have only got 3 days under our belt).

Cons: Because the harness was not quality checked it cost us a bunch of time and hassle to figure out what was wrong.


Written By CA Tunes, California on Sunday, September 13, 2015

Crutchfield Customer Review (What's this?)

does as described, easy install

Pros: retains factory functions

Cons: none

Don't waste your time

Written By JohnO, Texas on Friday, September 11, 2015

Crutchfield Customer Review (What's this?)

My initial thoughts when I opened the package was the product was cheaply made and the plastic pieces were ill-fitting. After spending an hour soldering every wire to the aftermarket radio, I installed the radio in my vehicle. The radio powered up and I began to test the functions of the radio to make sure everything worked. There was no audio no matter what I tried. I double checked all the connections and everything was correct. I called Crutchfield and spoke with a technical advisor. He instructed me to try several different things, still with no avail. He advised he would send out a replacement and I should receive it in the next several days. I asked if there was another product available. He advised we could try the PAC5. When I received the PAC5, I was impressed with the packaging and the strict tolerances of the plastic housing. I was more impressed that all the settings are done at the factory (all I had to do was adjust 2 screws to set chime volume and set the mode for my Kenwood Radio-extremely simple to do). The GMOS-04 had numerous settings that needed to be made and still didn't work. Save yourself time and headaches...avoid the GMOS-04 at all costs. The PAC5 is a much better product and as close to plug and play as anything out there.

Cons: Cheap Plastic Housing Too many settings that need to be done manually

Product worked as expected

Written By TL, Pittsburgh, PA on Thursday, August 27, 2015

Crutchfield Customer Review (What's this?)

This product worked well and as expected.

Made For An Easy Install

Written By js, New York on Friday, July 24, 2015

Crutchfield Customer Review (What's this?)

Retained all the oem features...Accessory Power,On-star,Chimes,Bose and factory amp,Had no problems with instructions and they were straight forward and very clear for my application

Pros: Retained all factory functions i needed,Made for a very easy install.

Cons: Little wire matching involved hooking radio harness to interface harness but not a big deal took 10 minutes and was well worth the time.

Had to call tech support

Written By cielosf, New Jersey on Thursday, July 16, 2015

Crutchfield Customer Review (What's this?)

First off I wish I had cut off at least four inches of wiring on the wires that get attached to the radio harness. When it was complete it was long and had to be wrapped and tied. I soldered the wires together and used heat shrink tubing so it came out neat and compact. If I had used crimp connectors especially the bell type there would not have been enough room to stuff all this back into the dash of a 2005 Corvette along with the GMOS-04 and relay. Had extra wires left over so I called tech support and went over everything with them to be sure all was correct . The pro's at Crutchfield were a big help. Don't hesitate if you have any doubt's as to what you are doing.

Pros: Harness works like a charm.

Cons: Certainly not plug and play.

Onstar or not Onstar?

Written By kkrueger, Plum City, WI on Monday, July 13, 2015

Crutchfield Customer Review (What's this?)

Adaptor plugged right in. I was on my own with the other end of the wires... the directions were more like "general guidance". Would have preferred more specific instructions. My car (2004 Grand Am) didn't have Onstar, so I am not sure why I got a kit for "maintaining Onstar".

Pros: Plugged in on the one end...

Cons: Did I really need it for my car because I never had Onstar?


Written By Anthony, Dover, MN on Monday, July 06, 2015

Crutchfield Customer Review (What's this?)

It works but is cheap had to glue it to keep together. Very cheaply made would go with pac next time

Pros: It works

Cons: It's cheap had to glue pins to gmos so all speakers stay working otherwise works but would have only paid half the price if I'd known it was that cheaply made unsatisfactory for sure

Aftermarket in 02 impala

Written By CT, Indiana on Wednesday, June 17, 2015

Crutchfield Customer Review (What's this?)

Allowed me to install aftermarket stereo and keep doorchimes and other features

Pros: Allows aftermarket install without keeping factory stereo in loop (other alternative would be to keep linked to system to reset warning lights but store in trunk)

Cons: Somewhat time consuming making connections, also seems I should be able to tune stereo louder than the dial allowed

Works great but confusing

Written By redflagharley, San Antonio on Sunday, May 31, 2015

Crutchfield Customer Review (What's this?)

This wire kit worked great but had my head shaking for a couple of hours! I had to remove and call tech support the next day to prevent from loosing it. Turns out it was simple just not the best instructions. The kit is for GM vehicles with the Bose and onstar features. My vehicle has the Bose but not onstar. This means there are several plugs and wires on the harness that just float around not connected and not used. Drives me crazy to have all those unused connections but it works!

Pros: Value, function, and options

Cons: Instructions are horrible

Important installation component

Written By OllieS, Longview, TX on Wednesday, May 20, 2015

Crutchfield Customer Review (What's this?)

This made the installation of the JVC KW-R710 head unit I got here happen easily. Only one hiccup in the wiring and that was easily fixed. The alert chime is much quieter then the original which I really like.

Pros: Very easy to hook up

Cons: Two wire colors are very easy to confuse.

Wiring interface

Written By LesS, Michigan on Monday, May 04, 2015

Crutchfield Customer Review (What's this?)

Good wiring interface and the tech support is super.

Pros: Great tech support for any problems.

Cons: None

Metra GMOS-04 Wiring Interface

Written By Anonymous, Granite City, IL on Sunday, April 12, 2015

Crutchfield Customer Review (What's this?)

Easy to install. Was very pleased

Thanks Crutchfield

Written By JR, Iowa on Thursday, March 26, 2015

Crutchfield Customer Review (What's this?)

Thanks for including this with the radio. Installation was easy!

Pros: Installation was easy.

Cons: .

Metra VT-GMOS-04 Wiring Interface

Written By Jerry K, Minnesota on Thursday, March 19, 2015

Crutchfield Customer Review (What's this?)

This product was extremely easy to install and use with a slight amount of technical know-how. The instructions that I got were a bit unclear (I may not have read them all) in how to splice this harness into the aftermarket radio. I ended up cutting the wires and splicing the radio harness into this. Once all was said and done, it worked really well!

Metra VT-GMOS-04 Wiring Interface

Written By TKS, North Carolina on Wednesday, March 11, 2015

Crutchfield Customer Review (What's this?)

The interface was easy to install. It was more than I needed but at least XM radio can be connected it needed in the future. All other features were transferred and work perfectly.

Pros: Everything was easy to connect and worked as advertised.

Cons: Did not need all the functions it was designed to transfer. A less functional, cheaper adapter would do the job.

Harness Installation made Easy

Written By Jason1, Agana, Guam on Saturday, February 28, 2015

Crutchfield Customer Review (What's this?)

Product was easy to work out and connect together. I would recommend carefully reading the directions just to ensure you do not connect the wrong things together. The color coding for all these units helps make it easier but just be careful. Overall very happy with the product and the ease with which to

Pros: Easy install

Cons: None so far

Easy Install

Written By Troprice, Texas on Saturday, February 28, 2015

Crutchfield Customer Review (What's this?)

Installed this with my New Pioneer Navigation unit. This made for a very easy install as all the wires are color coded or are outlined in the directions. It was simple to integrate the steering wheel adapter i purchased. Everything was a simple plug and play after soldering all the wires to the units wiring harness. Works much better than the PAC Interface that was installed with previous unit, which malfunctioned for no reason after 2 years.

Pros: Simple Installation

Cons: None

Ok item

Written By bigjohn, ga on Thursday, February 26, 2015

Crutchfield Customer Review (What's this?)

It doesn't do my door chimes all the time the right way but keeps my bose system so I'm happy

Pros: Keeps bose

Cons: Finicky with door chimes

Metra wiring device

Written By Kim R, Chicago Illinois on Thursday, January 15, 2015

Crutchfield Customer Review (What's this?)

Just as advertised

Pros: Chime sounds cheap

Cons: Works perfectly

Metra VT-GMOS-04

Written By Ben, Harlingen, Tx on Tuesday, January 13, 2015

Crutchfield Customer Review (What's this?)

Installed on my 2005 Tahoe great up grade. Like everything about it. Works well

Pros: Does what it's suppose to do

Cons: None

Worth the extra Cash

Written By John C, Arkansas on Saturday, January 10, 2015

Crutchfield Customer Review (What's this?)

The Metra VT-GMOS-04 Wiring Interface works as advertised. Just follow the instructions and connect the wires by color and your set. The chime and audio volume can can be adjusted to your liking. I installed it on a 2003 Chevy Silverado.

Best option on the market

Written By John T, Hampton, VA on Monday, December 29, 2014

Crutchfield Customer Review (What's this?)

Best option on the market that I could find

Pros: Ease of install

Cons: none

Metra VT-GMOS-04 Wiring Interface

Written By Anonymous, Tennessee on Sunday, December 28, 2014

Crutchfield Customer Review (What's this?)

The Metra VT-GMOS-04 Wiring Interface is a great addition to add when installing a new radio.

Pros: -Clear sound and just works

Cons: -Way to many wires. -must be soldered together.

Metra GMOS-04 Wiring Interface

Written By Anonymous, NY on Sunday, December 28, 2014

Crutchfield Customer Review (What's this?)

It works ok, I don,t use On Star so I can't comment on that part.

Pros: Ok

Cons: To many wires to hook up, directions could have been better.

Works great

Written By Rj, Sunshine state on Friday, November 28, 2014

Crutchfield Customer Review (What's this?)

I ordered the wiring interface and steering wheel adapter together. I'm glad I did they work perfectly. Everything works great.

Pros: Easy to install

Cons: None


Written By Brotherwind, T or C NM on Thursday, November 13, 2014

Crutchfield Customer Review (What's this?)

Crutchfield team was excellent. After getting wrong part from other dealer these guys cleaned that guys mess up. Works perfectly. Took but minutes to install. No problems. Rain sensors still working fine , don't use onstar but it seems like it's properly powered up. Doesn't allow all 6 speakers to function , but that's Bose's stuff. Will definitely go with these guys. Prices as good as anywhere else. Fast delivery. Even emailed me our online chat conversation which is nice so everything is open. Thanks Crutchfield...

Pros: Quick and easy install. Everything works. Quick delivery. Excellent team work.

Cons: The Bose system will not allow this harness to utilize all 6 speakers. Not their fault , it's a Bose thing I'm told by installer.

Metra GMOS-04 Wiring Interface

Written By Anonymous, Rockland, MA 02370 on Tuesday, November 11, 2014

Crutchfield Customer Review (What's this?)

Really made installation easy.

Didnt work

Written By Charlie, Mt on Wednesday, November 05, 2014

Crutchfield Customer Review (What's this?)

Just spent almost $300 on new stereo and this item to make it work. Confusing to install and ended up mutilating it, so unreturnable. So now have a torn up car and down almost $300.

Metra GMOS-04 Wiring Interface

Written By Bdubtex, Memphis, TN on Thursday, October 02, 2014

Crutchfield Customer Review (What's this?)

Works great

2007 Chevy Silverado 1500 with Bose

Written By Anonymous, Illinois on Friday, September 26, 2014

Crutchfield Customer Review (What's this?)

Used on an 07 Silverado with bose speakers and a JVC KW-R910BT head unit. Works great!! Customer Service was beyond excellent as I failed to order this with the HU but no problem. Recieved in 3 days and even got the special price, 1/2 off, that I would have recieved if I would have ordered both together, instead of being charged full price. :-)

Pros: Everything!

Cons: None

Perfect interface for my Suburban

Written By Paul, Houston, TX on Wednesday, September 24, 2014

Crutchfield Customer Review (What's this?)

It works and easy to install.

Metra VT-GMOS-04

Written By Jorge, Haines City, Florida on Friday, September 19, 2014

Crutchfield Customer Review (What's this?)

Plug and play, no issues

Cons: Too bulky

Good Product

Written By DCP, Houston, TX on Tuesday, September 02, 2014

Crutchfield Customer Review (What's this?)

This product is a bit intimidating to look at, but the instructions are reasonably clear and it works as advertised for what I am doing with it. I am using it only to connect to a Bose amp. I cannot comment on the other functions.

Pros: Facilitates an aftermarket head unit to a Bose amp. Sets itself up. Unlike competitive product, it allows the fader to work.

Cons: Bulky with a lot of wire to move out of the way during installation.

Metra VT-GMOS-04 Wiring Interface

Written By KellyK, Georgetown, Tx on Thursday, August 28, 2014

Crutchfield Customer Review (What's this?)

Wiring harness works great. The wiring instructions were easy to understand. My only complaint is that there needs to be some additional info on using the ASWC interface.

Pros: Clear and concise wiring instructions.

Cons: Needs additional elaboration about using the ASWC interface with it.

Metra GMOS-04 Wiring Interface

Written By Anonymous, Roanoke Va on Wednesday, August 06, 2014

Crutchfield Customer Review (What's this?)

Was not a good unit

5 stars!

Written By Wyatt, Edgerton, MN on Saturday, August 02, 2014

Crutchfield Customer Review (What's this?)

Great purchase, easy install and lives up to its perks!

Pros: Easy install

Wiring harness

Written By MikeH, Tulia, TX on Saturday, July 26, 2014

Crutchfield Customer Review (What's this?)

Works very good in 2004 Silverado 1500

Pros: Easy to install

Cons: Too many red wires and no explanation which one goes to what.

GMOS-04 adapter cable

Written By zbee062, Anderson, SC on Tuesday, July 22, 2014

Crutchfield Customer Review (What's this?)

I recently purchased a DNX890HD to replace an older unit in a 2008 non-Bose Corvette. The instructions were reasonably clear and I successfully spliced the adapter and the 890 unit together and everything worked first time. This included rear and forward facing cameras, OnStar (no subscription but music correctly muted automatically while listening to the recorded message). The nav screen automatically switched to the rear facing view when reverse was selected. The HD radio worked very well, as did an iPod, an MP3 player (via the Kenwood KCA-IP202 cable) and an iPhone 4S via the 890 built in Bluetooth system. The speakers could be controlled as per input to the 890 unit. Chimes worked correctly when the door was opened in accessory mode. Did not test other possible alerts. Had to read instructions closely several times to catch that the GMOS-04 cable red wire connects to the red wireS (i.e. both?) from the 890 unit. Including the word "both" red wires would have saved some time trying to understand which red wire to use. Per comments below one red wire should be connected to the steering wheel controls which was not used on this installation.

Pros: Instructions were good and easy to follow. I found it useful to read other reviews in various forums before splicing the cable to gain a better understanding of any potential problems that may arise (there were none for me).

Cons: None except it looks a mess when everything is connected, but that is hidden from view when installed. Only tested for one day in the car as the Nav system failed ("no maps available") , nothing to do with the cable but it prevented longer term testing as the 890 unit was returned.

Metra GMOS-04 Wiring Interface

Written By Anonymous, Lexington, Kentucky on Monday, July 14, 2014

Crutchfield Customer Review (What's this?)

Very complicated with poor instructions

Nice unit

Written By Anonymous, Lincoln Ne on Tuesday, July 01, 2014

Crutchfield Customer Review (What's this?)

Straight forward wiring

Does what it's supposed to do...

Written By S, Kansas City on Tuesday, June 03, 2014

Crutchfield Customer Review (What's this?)

Works perfectly in my 2002 GMC Envoy.

Works with a little intervention.

Written By Allen E., Oswego, IL on Monday, April 28, 2014

Crutchfield Customer Review (What's this?)

Not a difficult install if you can handle a soldering iron and read. Unfortunately the directions were not 100% accurate. Probably i the nature of a "universal" adaptor. Had to experiment a little with the wires that were supposedly "not used". Head unit didn't receive power at first after follwoing teheir instructions. Turned out that the three wires that were to be "cut" and not used, 2 had to be reconnected for the head unit to function. So far works fine . . . with a little ingenuity on my part.

Pros: Works.

Cons: Not perfect instructions

Metra GMOS-04 Wiring Interface

Written By Anonymous, sonora, Tx on Monday, April 21, 2014

Crutchfield Customer Review (What's this?)

It works good, it does what it supposed to. The only concern I had was during installation there were two bat. Red wires, now were both of those wires supposed to be connected together or was just one supposed to be connected. I connected both of them together to the12v source wire. Should I leave both of them connected or go back in there and just leave one connected?

Crutchfield response on Wednesday, April 23, 2014 One of those red wires is meant for powering the optional ASWC-1 adapter for the steering wheel controls. Our tech support team followed up with the customer to let him know.

Easy install... Easy life

Written By MisterBond1989, Adelanto on Thursday, April 10, 2014

Crutchfield Customer Review (What's this?)

This adaptor is awesome! Makes things easy to install another radio. No cutting or splicing of wires. Only one issue that I have found while using this product is that the factory Monsoon amp in the 1999-2005 Pontiac Grand Am does not get bypassed. If you have a Monsoon equipped Grand Am; the factory external amp needs to be used in order for the factory speakers to work. This makes sound quality very poor and low. If this is the case for you, I suggest installing an external amp and get rid of the Monsoon amp. Beside that issue; great product!

Pros: Makes install of radio easy, clean, and worry free. No cutting of the factory wires needed.

Cons: Does not bypass Monsoon amp in the 1999-2005 Pontiac Grand Am.

Does it's job

Written By JYaz, Hanover, PA on Thursday, April 10, 2014

Crutchfield Customer Review (What's this?)

It does what it should

Pros: It works

Cons: All of the wires are confusing. Instructions aren't the best.

05 gmc truck upgrade

Written By Doug H, Charleston S.C. on Tuesday, March 25, 2014

Crutchfield Customer Review (