Metra 70-1857 Tuner Relocation and Bose Integration Harness for Select GM Vehicles

When I got this, I didn't quite understand what it does. This harness completely replaces the head unit and the CDM receiver box. You can throw both of those away. What it keeps are the amplified Bose speaker system. What this means is that the speakers each have their own amplifier and they are expecting to receive as input, low level RCA (like microphone level) signals. There is still a relay in the system which is turned on by the blue wire that powers these amplifiers. I had a problem with my car where that relay wasn't working, so no sound was coming out of the speakers because they were not powered. To check if this is working, take the grill of a back speaker and unplug the wiring harness. Put a meter on the orange and black wire. When the radio is on, you should see 12 volts. If you don't see that, then your relay is busted and you have to get that fixed first. For most aftermarket radios, this blue wire will be on whenever the ignition is on. This will also raise the power antenna and basically, your antenna will be up anytime the ignition is on. Even if you turn off the radio, the antenna may still be up (depending on how your radio implements the blue wire). This is a disadvantage compared to the stock radio where the antenna will go down if you turn off the radio. Getting back to what the harness does. Your aftermarket radio should have RCA low level pre-amplifier outputs. The harness connects these up to the speakers directly. The blue plug goes to the front speakers and the white plug goes to the rear. The red plug supplies the power and the all important "blue" wire. The other 2 plugs on the bottom of the CDM go to the old head unit and are unused. The problem that I found with this harness is that a lot of noise from the engine and the Android head unit itself gets into the low level signals inside the receiver (especially cheap Android units like Hipzo) and so you can clearly hear your engine RPM through the radio. This is extremely annoying and unacceptable. This can be fixed by getting a line level adapter like the Scosche SLC4 which is pretty cheap $13 on Amazon. You might as well get one because I suspect the noise problem is very common and unavoidable with this type of system. This allows you to plug into the full power speaker connections which are not vulnerable to this type of noise interference and reduces the signals back down to RCA level which is what the Bose speakers expect. This gets rid of the engine noise and loud pops when turning the receiver on/off and other annoyances. If you are getting this for a C4 corvette, there is probably going to be a lot of cutting to fit the double-din because it isn't the right size for a standard double din. You're also going to need the aftermarket mounting brackets as the Corvette mounts are extremely funky. To run the wire to the back, you're going to have to take out the center console and the passenger seat to remove the tunnel panels. If you can do all that, then this harness will allow you to run your aftermarket radio with the existing powered Bose speakers - which actually sound pretty good to me.

Cables are extra long like everyone said before me. I put exess in cable in compartment behind passenger seat.This eleminates head unit and the little tuner box in compartment. Amps are attached to speakers. I used RCA jacks. Dont buy the Scosche thing like first guy said if your using RCA jacks. If not then yes get that. You will need a RCA ground loop isolator to get rid of pop and noise. Also, dont buy the extra antenna adapter that amazon wants you to buy. This cable harness plugs into both ends of the system without adapters. Start in rear when running wires.

Installed this into a 1992 Corvette. Worked great. My only complaint is the length of wire you get. I ended up stripping them to shorten them up because there was no way I could store the wires otherwise.

Perfect harness but if using for the older cadillacs that had the factory bose (where each speaker has its own amp built on it) you will get noise when you turn on the car... The first step is getting 2 ground loop isolators.... That takes care of the 'pop' between tracks or switching stations.... The next thing you will have to do is a bit of rewiring in the trunk where this plugs in. Note.... If you are not an installer then this won't make any sense..... The problem is the pop from the stereo turning on... So you need to use the red wire in the trunk (on this harness to turn on the amp) which is the blue wire on the harness..... The blue wire coming from the head unit needs to still trigger the power antenna but also needs to trigger 2 relays. The 2 relays need to be separating one of the speaker wires at the rear speakers.... For example.... 85 goes to ground 86 goes to the remote wire off the deck 87 goes to the speaker and 30 goes to the amp side of the speaker (basically you are separating the speaker wire until after the radio comes on... Then the blue wire will activate the relays to let the speakers come on.... Essentially after the 'pop' would happen) it's a timing thing and that is the only solution short of rewiring the whole car. Now I know that doesn't make a whole lot of sense but it will if you are an installer... You will get the point.

This comes with extremely long set of cables which is good. This fit for my C4 Corvette 1992. For this working on the same vehicle, you do not use the cables behind the factory radio to plug into this harness. You have to unplug the cables from the ECM under the passenger dash/glove box and plug those cables into this harness. Then run the wires back to where your after market radio will be.

Easy Install and a mustif you want to upgrade to an After Market Radio.

Does what it's supposed to do but for someone who hasn't worked with Bose before some instructions would be nice. Once we figured things out all went well although the amount of wire and coax required substantial cutting and soldering to avoid excess wire coils stuffed out of the way. Bottom line, it's a good product which makes a job that could overwhelm the the inexperienced manageable.

I installed this cable in my 1996 corvette equipped with factory Bose speakers,the harness seems to be good quality and works as it should,but after installing everything the speakers make a pop noise when I turn stereo on or off,(common problem i find out now.) I don't think it will harm anything but its annoying. So next I'm gonna try a 4 channel ground loop insulator connected between head unit and harness and see what happens.

Top quality , very reasonably priced,considering the cables are 18 feet long.

Best