Metra 70-1856 Bypass Harness

Allows you to connect a new car stereo to factory wiring in select 1990-96 GM vehicles with non-Bose® systems

Item #: 120701856

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7 Reviews

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This Metra 70-1856 bypass harness lets you replace the factory radio in select 1990-96 GM vehicles without the factory Bose® system, using the existing wiring and connectors. This harness bypasses the remote tuner in certain vehicles. Warranty: 1 year.

Please enter your vehicle information or call an Advisor at 1-888-955-6000 to find out if this model is compatible with your vehicle.

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 70-1856 Bypass Harness Reviews

Average Customer Review:

7 reviews
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The bomb ,this made my installation go perfect thx Crutchfield!

Written By Razor, Michigan on Wednesday, June 17, 2015

Crutchfield Customer Review (What's this?)

Needed this item it was a lifesaver

Pros: The best

Cons: None

Effortless...Does the job

Written By sjCohen, Wisconsin on Monday, April 13, 2015

Installed in a 1995 Cadillac Seville SLS. Known to be an absolute "pain in the foot" to repair (even GM mechanics complained which brought a complete re-design by GM two years later), installing this wire harness was not only painless, but effortless. Extremely well made.

Pros: Easy Install, Quality Product

Cons: None

Harness adapter

Written By Pablo, Wi on Friday, May 02, 2014

Crutchfield Customer Review (What's this?)

Used for a 1994 fleetwood and made installation a breeze. I wrapped it in electrical tape to keep it all together during i stall

Pros: Makes DIY car installation easy

Cons: NONE

Makes the job soooo easy!

Written By bigjim, Sparta, TN on Friday, April 04, 2014

Crutchfield Customer Review (What's this?)

Made the install of my new Kenwood DDX471HD so easy, it is a must have for anyone.

Pros: easy to install, great quality

Cons: NONE!

1993 Vette Wiring Harness

Written By D01ATC, Denver, CO on Thursday, May 23, 2013

Crutchfield Customer Review (What's this?)

This wiring harness was a lot if wire, probably about 10-12 feet worth. Had to obviously trim some, but got the job done.

Pros: Plenty of wire length.

Cons: Simply to much wire.

Metra 70-1856 Bypass Harness

Written By Chris L, Greensboro NC on Thursday, February 09, 2012

Crutchfield Customer Review (What's this?)

This wiring harness does not match that of my 1993 Cadillac Sedan Deville,therefore can not use radio. It is missing one port.

Pros: Have none at this time.

Cons: Not functional.

You Need This

Written By TechLauren, Milwaukee/Madison, WI on Monday, May 09, 2011

You can buy this or make it and it's going to be such a bear to install this
wire bundle that you may as well give yourself a little break and buy this part.
I installed mine in a 1995 non-bose Eldorado. The installation instructions were
too general and I had to ask for help on the Cadillac Forums. The harness
plugged into my CDM box in the trunk by the power antenna and the other wires
all mated up perfectly with my new radio once I got them routed to the front of
the car. There is was no way to install a modern head unit in my car without
this part so I give it 5 stars as it was required and not optional for me. I
ordered a crimper with it to get free shipping lol. I have photos but no video
of it.

Hands-on research

What's in the box?

Download owner's manual

  • Receiver wiring harness (includes antenna)

Product Research


Crutchfield Wiring Harness: Crutchfield wiring harnesses prevent you from having to cut your vehicle's factory radio plug when replacing your factory radio with an aftermarket head unit. Simply solder or crimp the Crutchfield wiring harness to your aftermarket head unit's harness (solder & crimps not included), plug the aftermarket head unit's plug into the rear chassis of the aftermarket head unit, and plug the Crutchfield wiring harness into your vehicle's factory radio plug.

Note: Installation tools, hardware, & accessories are not included & sold separately. Please see the Accessories tab for recommendations & availability.

Wiring Notes: If the Crutchfield wiring harness is not equipped with a ground wire, you will need to ground the aftermarket head unit's ground wire to the metal chassis of your vehicle. Some vehicle's may require you to bypass the vehicle's factory amplifier (in another location from factory radio) or hardwire certain connections. If your vehicle is equipped with factory steering wheel controls, an additional adapter is required and sold separately.

Wire Code Chart:

Wire Color Function
Black (thick gauge) Antenna cable
Red +12 Volt Accessory
Yellow +12 Volt Constant
Black Ground
Blue Power Antenna/Amp Turn-On
Orange/White Dimmer
White Left Front Speaker +
White/Black Left Front Speaker -
Gray Right Front Speaker +
Gray/Black Right Front Speaker -
Green Left Rear Speaker +
Green/Black Left Rear Speaker -
Violet Right Rear Speaker +
Violet/Black Right Rear Speaker -

The Crutchfield Car Selector: Please visit the Crutchfield Car Selector for your specific type of vehicle.

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.

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