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Scosche C4MA02 Factory Integration Adapter

Allows you to connect a new car stereo and retain the Bose® audio system in select 1993-up Mazda vehicles

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  • Scosche C4MA02 Factory Integration Adapter

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Our take on the Scosche C4MA02 Factory Integration Adapter

by Charlie Pastorfield
Scosche

The Scosche C4MA02 OEM Amplifier Adapter is a non-electronic interface package that allows you to integrate a high-powered aftermarket receiver into select 1993-up Mazda vehicles with premium factory systems. The package includes the OEA-4 adapter and a Mazda-specific harness. The OEA-4 unit has output-level gain controls for each of its four channels which can be adjusted to properly match the new receiver to the factory amplifier.

Note: If you haven't already, please enter your vehicle information or call a Sales Advisor at 1-888-955-6000 to find out if this adapter is compatible with your vehicle.

Details:
  • 4 speaker-level inputs
  • output level adjustments for all four channels
  • works best with high-powered aftermarket receivers
  • dimensions: 3-15/16"W x 15/16"H x 2-1/16"D
  • 1-year warranty

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 from the Crutchfield Labs (what are the Labs?)

Product Research
What's in the box?

Download owner's manual

  • OEA-4 OEM Amp interface (with 8-wire input with bare wires/8-wire output with 2 white rectangular connectors)
  • Flat-blade screwdriver (attached to interface module)
  • 13 Crimp caps
  • Instruction sheet

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 open the box, verify contents, 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.

Features

Compatibility: The OEA-4 (model C4MA02) is a non-electronic interface that allows an aftermarket high-power stereo to integrate into select 1993-up Mazda vehicles with Bose premium factory systems. Please check the Crutchfield Vehicle Selector for compatibility for your vehicle.

Adjustment Gain Controls: Four rotary gain controls (front left, front right, rear left, rear right) are located recessed inside the adapter chassis. There is a small flat-blade screwdriver attached to the adapter's case, and its use is recommended. The controls are very fragile and sensitive, and a slight adjustment will change volume dramatically.

Harnesses: The adapter's input wires are approximately 5-1/2" long with bare ends. These splice to the new receiver's speaker output wires. The adapter's output wires are approximately 11" long and terminate into two white rectangular Molex plugs. There are 4 additional wires coming from one of the white plugs that should be spliced to the receiver's wiring harness. The Molex plug ends are molded to match with the factory wiring harnesses. Crimp caps are provided for wire splices.

 
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Scosche C4MA02 Factory Integration Adapter Reviews

Average Customer Review:

14 people say:

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4 out of 5

Scosche review

Written By GrayDD, Alvin, Texas on Tuesday, December 31, 2013
Crutchfield Customer Review (What's this?)
 
Used to connect a Kenwood system to an existing factory Bose speaker system in my Miata. Over all pleased with the outcome however the instructions for installation were severely lacking and a call to tech support was required. Tech support was fantastic and had me squared away in minutes.
Pros:
Sound quality was awesome and adjustable features were just what was needed.
Cons:
Installation instructions were not good to say the least. (was not plug and play) had to cut and splice into the factory wiring, which is exactly what I did not want to do. Kind of defeated the purpose of buying a plug and play adapter. Was not that big of deal as tech support got me on target right away.
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4 out of 5

easy to install, but not complete

Written By JasonF, Atlanta, GA on Sunday, June 02, 2013
Crutchfield Customer Review (What's this?)
 
Worked great to add a JVC head unit to my miata, but had to change a pin to make the amp work... and if it is made for a miata, I only need two channels (If it could've been smaller), real estate in the dash is rather tight. But wiring it to the JVC harness was simple and quick. It made installation simple!
Pros:
color coded, easy to use
Cons:
could've been a two channel model, and prewired for the amp on/off - if I could adapt it so easily, why not just offer a version?
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2 out of 5

Scosche adapter

Written By Dave E, Grass valley, CA on Monday, May 20, 2013
Crutchfield Customer Review (What's this?)
 
The reason for the "two stars" only has to do with the workmanship on the product. The wire splices made by the manufacture were terrible. The crimps were loose and one was completely detached. I first called Crutchfield to get a replacement, but was told it would take another week plus to get the replacement. The tech at Crutchfield was not the most helpful personal. He told me "me just sell these we don't make them!". I chose to keep the bad unit and repair it my self. I cut out all the splices and redid the connections with solder. The unit work well, once repaired, and I can say I am happy with it. Just be prepared to fix this product if you should order it.
Pros:
Works after repair
Cons:
very poor quality control on workmanship.
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3 out of 5

Missing a pin

Written By Turborascal, Austin, TX on Monday, July 23, 2012
Crutchfield Customer Review (What's this?)
 
Somewhat bulky, this unit does the intended job after moving a pin to power the factory Bose amp with unit powered-up. I'm disappointed that Scosche fails to provide separate pin-outs to independently trigger the power antenna and power amplifier. If following their instructions, the antenna would go up whenever the head unit is on, rather than with the tuner only. Fortunately, this was installed in a Miata that lacks rear speakers. Speaking with Crutchfield tech support provided the correct factory harness pin to trigger the power amp. Moving a pin/wire from an unused rear speaker position to the correct location allows the head unit to turn the amp on without having the antenna rise; while the antenna rises when the tuner is selected. This product needs to provide connections for all permutations of factory equipment without the need for modification. That said; it works once modified.
Pros:
Does the intended job.
Cons:
Bulky, fails to provide separate trigger pins/wires for power antenna and power amplifier. Must be modified to properly work with both.
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3 out of 5

Works fine - needs update to work for the Miata

Written By Nick P, Minneapolis, MN on Tuesday, May 22, 2012
 
Overall, this unit works as intended. As others have said, it's not plug-n-play -- you need to splice some wires to connect to the Bose amp. The tech support at Scosche found the issue on the first call and was able to remedy it.

I wish the wires were longer so that I could relocate the adaptor to the glove box. As is, it's tucked behind the double-din head unit, which makes any adjustments very diffficult.
Pros:
Works great
Cons:
Poor instructions. Short wires mean adjustments after install are very difficult.
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4 out of 5

Works like a charm

Written By JayBee, Charlotte, NC on Friday, September 16, 2011
Crutchfield Customer Review (What's this?)
 
I was putting a Kenwood KDC-X595 head unit in a 1999 Mazda Miata with the factory Bose system. The integration with the Base system forced some adaptations, and the Scosche worked like a charm after installation. I was replacing a double DIN unit with a single DIN unit, so I had lots of room. That meant it wasn't at all difficult to dial in the settings which you must do with the radio in operation. If the placement was tighter, it might have been much more challenging. My only suggestion -- make the wires long enough so the Scosche unit can reside permanently in the glovebox and easily be reached for tuning after buttoning up the installation, instead of putting it behind the head unit where it is now unreachable until the end of time.
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3 out of 5

Missing amp power lead

Written By Badbob 19919, Seattlle Wa on Saturday, September 03, 2011
Crutchfield Customer Review (What's this?)
 
Product works great except theres a missing pin for the amp power so had to do some splicing. Also product kinda big ,didnt really need a 4 channel ,2 ch would have been 1/2 the size.Thought about cutting it in half
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4 out of 5

99 Mazda Bose System Patch

Written By Scott S, Seattle Wa on Wednesday, June 29, 2011
Crutchfield Customer Review (What's this?)
 
This device scales the output of the main deck befre going into the inputs of another source. In my case I chose to keep the Bose speakers and amplifier that came with the 99 MX5. I cut off the harness for the rear speakers since there none in the MX5. The only issue was the power lead for the Bose amp was missing. I had to take one from the connector I cut off and insert. Then it worked great.
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1 out of 5

Worked, but not without modification.

Written By Scott B, Austin, TX on Monday, May 23, 2011
 
The Scosche adapter did not include a connection the the power-control wire that activates the factory installed Bose amplifier. It took several phone calls, and it was Crutchfield service that finally came up with the solution.

I had to remove the control wire from the factory harness and connect it to the P.CONT wire of my Kenwood receiver.

Not that this was extremely difficult to do, but it is a significant oversite on the part of this adaptor to leave that wire in the harness without a companion wire in the adaptor plug. Add to that no instructions on this wire and the fact that Scosche had trouble diagnosing why I had no sound in my speakers, and I have to give this product an unacceptable rating.
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4 out of 5

Product Great, Instructions lacking one key thing...

Written By David W, Nashville, TN on Sunday, May 22, 2011
Crutchfield Customer Review (What's this?)
 
2000 Miata SE w/ Bose AM/FM/Cassette replaced w/Pioneer Double-DIN unit

Product performs as described, box is big to hide in the dash, but creative stuffing makes it all fit. Would be nice if they offered a 2-channel version seeing as I cut the rear cables to make room. One big issue, this harness did not provide a pin for the Bose Amp "on" sensor. As described by the other reviewers, we needed to add, splice or weld a connection from the radio to the Bose amp switch (so the amp would turn on when you turned your new head unit on.) This was not in the instructions (very un-Crutchfield like.) You guys have spoiled me in the past with flawless step-by-step instructions. This time there was a "gap."

A little searching on the miata-dot-net forum provided a description and pictures on how to add the "amp on" wire. When you buy this product, search for this topic "Keep your Bose Speakers and Replace Head Unit" and you'll be set!
4 out of 4 people found this helpful
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4 out of 5

It works, but it took some fiddling

Written By Paul G, San Jose, CA on Monday, March 07, 2011
Crutchfield Customer Review (What's this?)
 
I got the setup for a Mazda Miata with Bose amplifier. It works quite well,
once it's installed, but it took some fiddling with the help of the Miata online
forum to get the wiring harness right. That being said, Crutchfield's service
support was quite good, and the tech rep was able to confirm what wire needed to
be rerouted.
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3 out of 5

more information - less calling

Written By Anonymous, Pittsburgh. PA on Saturday, August 07, 2010
Crutchfield Customer Review (What's this?)
 
After 4 calls to the vendor for technical support, which could have been spelled out in the minimal instillation information page provided. This adapter works, I guess, fine because the radio purchased and installed at the same time sounds great.

Just an installers note: If you want not to have the power antenna in the up position all the time, place a small switch inline on the power antenna sense wire, when your using the AM/FM throw the switch, when your using the CD/AUX port turn it off as it originally would do in the OEM radio. This was installed in a '01 Mazda Miata SE with the Bose Stereo system.
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3 out of 5

Scosche C4MA02 Factory Integration Adapter

Written By Marlin, N.E. Ohio on Friday, October 03, 2008
Crutchfield Customer Review (What's this?)
 
I bought this adapter for my Miata. It works fine, and the install is almost dummjy proof. The only problem is that there is not a power wire for the Bose amp inb the car. Since my radio doesn't have a dimmer feature, I just relocated the dimmer wire to the amp feed location. Viola! Works like a champ. I can even drown out the wind noise with the top down!
2 out of 2 people found this helpful
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3 out of 5

Hey it works but could be better

Written By Brian, New Jersey on Wednesday, May 10, 2006
Crutchfield Customer Review (What's this?)
 
The Good:
This item will allow you to keep your bose amp working in a miata because it can transpose an amp'ed signal to a line level out put. The item in the picture is exactly what you get.
The Bad:
This item is not designed for the miata. It is designed for a car with four channels of audio. It is called a four channel car because it has component tweeters with built in crossovers (which are located in the door). So as you can see in the picture there is an adapter coming off the main conector which has two green and two purple wires, these are the rear channels. This entire connector and wires are completely useless-left floating in the consol. Further the bose amp needs to tap into the 12 volt aux power wire to power the bose amp. (or you get no sound) This wire is the little mint green 22AWG. it connects to the factory harness but this item does not connect to it. there is an empty hole where they should have put another wire. The only way you can tap into this power is to put a 'pinch' and crimp into that little wire (not easy since its in the center of the cluster). There are other wires my install left with no use too. But those are the main issues. If you have a two channel system like a miata, don't get this item. There are similar two channel devices out there. This item is based on the Ven 4 (4 channel model) the Ven 2 is all you need.

If you are installing Alpine IVA-D310 you don't even need a line level adapter. The D310 RCA line level output for amps.
69 out of 80 people found this helpful
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