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02/Factory AMP Bypass-A Simple Fix/great Results


New Member
Randy, I had to make changes in the wiring but it was not difficult.  The plastic wire/plug support had to be removed to facilitate wire removal and replacement and replacing the plastic support.  The wiring went as so: A1 to A9, etc. and B1 to B9, etc.

It worked the first time but the next time the no sound (except for the RF speaker) problem returned.  This leads me to believe it is in the radio or its connector(s).  A good thump on the dash momentarily interrupts the sound in the RF the only speaker that works (which is lousy anyhow).  The volume control was not very responsive.

I suppose I will have to opt out of this forum and try a forum dealing with the 2002 Avalanche radio and the difficulties in testing, removal, and replacement including availability and cost.

Can you direct me?

Bud :E:


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Good to hear the Metra 70-2021 works but you have to relocate some of the pins. That's still easier and cleaner that than using the 70-2002 and cutting, splicing and moving pins.

As far as your radio not working, if your sure it's the radio and not bad speakers. There are forums in the audio/video section that will help you to find a radio. You can replace you stock one with just about any aftermarket single din with an adapter or a double din with some modification.

I don't know if it's worth trying to fix you factory radio but if you want a stock one then you can pick one up at the junk yard or maybe someone with an 02 that has upgraded will jump in a sell you their old one..


New Member
Randy said:
Why not just buy the amp bypass from Metra.. 70-2021

Just got this from amazon and I can confirm it indeed does work. As budspwr has already mentioned, you need to move some pins around. It's very very simple, just grab a small paper clip, open it up and stick it into the holes above the pins. These are the holes I'm talking about: http://i.imgur.com/xpIuagL.jpg
Then lightly pull the cable on the other side back and forth while you're jiggling with the pin, don't yank or push too hard, you don't need to. Be patient and they will come out.

The cables on the Metra 70-2021 come configured as follows:

A1 to A12
A2 to A11
A3 to A9
A4 to A10

B1 to B11
B2 to B12
B3 to B9
B4 to B10

As you can see in this pic, each hole is numbered so it's stupid simple to rearrange the pins into the order we want: https://i.imgur.com/x6agFn9.jpg
Just rearrange them in the order shown by echastain88, they will click back in position:
echastain88 said:
It's much more simple than it seems. Get the metra 70-2002 harness Re pin the wires like so:

then un plug the lower plug in the factory amp and plug your harness into that plug. Boom done!
Additionally, unplug the upper plug and remove the garbage amp. When you pull it out, you'll find it's manufactured by a company called Matsu$hita (without the dollar sign). Says it all.  :p

My after market head unit outputs 40w to each speaker instead of 20w, so it should sound better at high volumes, I assume. At low volume I can't really tell the difference. Either way, I'm happy I removed an unnecessary middle man between the head-unit and speakers.

Thank you, thread.


Full Member
I know this thread is old but THANK YOU. 
I just had a cluster go out on my 2002 2500 Avalanche (I'm the original owner) and while I had that out to repair I decided to replace the burned out lights in the climate control and the radio.  Instead of repairing the radio lights I bought a double din Alpine iLX-W650 7" Mechless (it's only 2 13/16" deep), I also added a backup camera and a SirusXM tuner.  I found this thread and did the amp bypass and the sound improved quite a bit.  I will be adding an Alpine KTA-450 amp & speakers soon.  By the way the KTA-450 mounts on the back of the head unit and I still don't have to modify the radio bucket or the support, plus the radio kit came with a modified dash panel to fit the double DIN.  Those were reasons I never tried this before.

I bought the Metra 70-2021 bypass for the Monte/Impala and just rewired the one side using the pin out posted by hez it took all of 5 minutes.
- Dave

Black 2002 2500 8.1ltre  200,000+ miles, parts are getting harder to find but, Stayin' Alive
2 tranny rebuilds, one at 95,000 and the other @ 185,000 due to many, many miles pulling 12,000lb trailer