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

Welcome to the Magical Mystery Tour of GM wiring

UPDATE--DEC 02--
[ ?There is NOW an adapter available from you local car audio shop [Best buy-Circuit city] that mates to the Factory Amp input plug-- and stops you from cutting into the factory harness, as this original post described.
The after market harness, made by Metra #70-2002
is a unfinished harness and some crimping or soldering will be required--- further info on page 7 & 8 ]

If you replaced your HU and speakers and kept the factory wiring and amp, you are not obtaining maximun output
After my replacements, I still was not happy with the sound but determined to correct the problem
After bypassing the factory harness at the amp, you should see me smiling

Not quite sure what GM is thinking. they're trying to gain maximun output, thru ohms and a combination of series/ paralell wiring into the amp, which degragated the sound qualityand didn't really amplify

The factory harness colors to the speakers, have not changed in many years, but where they come from the head unit and to the amp, they do

The 8 basic door speaker wires are
TAN ? LF +
GREY LF -
LT GREEN ?RF +
DK GREEN RF-
DK BLU ?RR +
LT BLU RR -
BROWN LR +
YELLO LR -

IF YOU OPEN THE GLOVE BOX & FOLD DOWN
you will be looking at the factory amp
there are two plugs
the upper is the power lead plug [and possible sub outs, that have been determined to be non-powered ]
the lower plug is the spker wires [+ amp on ]
the upper part of the lower plug is the spker wire outs

Unplug both plugs from the Amp--
on the lower harness plug, this is were you will PERFORM THE METRA HARNESS BYPASS

Or-- If you are adding new speakers, you can run the new wires to the doors from the 70-2002 harness end and not tie the wires together

Now you have a clean signal from the HU


DUE NOT PLUG THE HARNESES BACK IN TO THE AMP
THE QUAILITY OF SOUND CHANGE is TREMENDOUS

Thanks to Gatorjedi for the wiring schematics
and others that have contributed

Thanks for the post. I will double check my bypass to be sure it was done correctly at Best Buy.

Hi Capecruis8der,
Did the wiring diagrams help at all? I have replaced my HU but not the speakers, and the main problem I have is the system is not nearly as loud as it was before the HU replacement. By the looks of it, your are bypassing the factory amp, basically jumping the speaker outputs of the stereo (that use to plug into the input of the factory amp) to the speaker inputs (that used to connect to the output side of the amp). I have always thought the factory amp was somehow undermining the power output of the aftermarket HU.
So how does is sound now that you have bypassed the amp? louder? clearer? more bass?

Thanks,
Gatorjedi

Great Hack!

Can someone else confirm that this is indeed highly recommend for anyone using the factory amp?

Thanks!

Great post Cape!

I agree that if you're not doing a whole system upgrade, just the HU, bypass the factory amp. With HU's as powerfull as they are today, and Delco's lackluster wierd amp system, it just makes sense. Did others experience volume discrepencies when cranking the volume on the factory system. Mine would actually get quiter...

Capecruis8der

I don't suppose you could take a few pics of this modification for everyone's benefit?? That would be most excellent.

Thanks...

Great find, I have been wondering how I was going to do this. I install some Crystal coax in the back and component in the front. They sound great even with the factory HU although I can hear a faint static sound between songs (BTW thanks CarreraRod for all the advice ).
I'll be upgrading my HU soon and want to bypass the factory amp so thanks again for the find Cape

Hey Joe, you decide on an HU yet?

Gator
yes the diag helped, once I figured out which ones were closer to the AV
you will need to do the speakers
after replacing the HU P75 and spkrs, Cerwin vega 6.5"R and pioner 6.75" F all I could get from them was a pop now it is very cleaner and much improved bass

and i'm sure if you ran all new wires from the HU to the spkrs in the door , you would get even a better bass
but that is a major job, this was simple

Also, I may atempt to put a small 2 channel up front to power the rears[I have ONSTAR]
because the harness has the HU turn on /power lead is right there

Has anyone that ripped apart the interior to replace the wires, found any Lt green/blk and Dk Blu/wite wires heading to the rear,
these wires are in the other plug for a sub output
Though, with the pathetic quality sound of the factory amp, I dont know if it would be of any benifit

Zimm
mine did as yours did
the louder you turn it the quieter it got,

B-mon
I will post pics as soon as I can find my bat for my digi-cam/been looking for an hour/looks like more money spent

Neophite here,
Can you just remove the factory amp and replace it with a better amp? Leaving the factory HU and speakers alone. All this splicing and ripping gives me a headache.

headbandman,

You'd have to get an amp that has high level (speaker level) inputs on it or get a converter to change the high level outputs on the factory HU to low level (RCA style) inputs for the aftermarket amp. Neither of these solutions is particularly attractive. Better to spend the extra cash replacing the HU and the amp at the same time so that it's an RCA to RCA connection (low level signal).

I haven't opened mine up yet for a look... after bypassing, can you actually remove the factory amp thereby making room for a small aftermarket amp in its place? I don't want any major changes and have decided against trying to do a sub (for now) so I just want to have good clean (maybe slightly more powerful) sound to the doors.

If the factory head unit has speaker level outputs, what happens if you bypass the factory amp and let the factory head unit drive the speakers directly? Is the factory amp the weak link in terms of sound quality? Is there enough power in the factory head unit to do the job?

I was initially surprised to find that the Av had an additional factory amp . . . not that long ago, all factory head units drove speakers directly! Has anyone tried this?

It took me longer to find the battery for my camera than to do this upgrade
pic link above

Big plug is spker wires
small to right is power and poss sub/tweet wires

Headbandman
My 2001 Pontiac Aztek has a 190W Factory amp by Pioneer
that was my first thought to
I had it out of the AZ in 30 Sec
looked at the plugs, they were the same
had a grin on my face, like I just got [*$&@] an AV
plugged right in too- got nothing
on closer inspection, all the wiring was different
different colors in different terminals
unfortunatly I dont have the schematic for the Az
probably could be done
not sure if the change was because it was Pioneer
Amp was prices at $210---bummer

wrchizm
on the wiring diagrams, it is listed as low spker level output /did not try to go direct
but i don't believe you would benifit, because when it comes out of the HU is were the wires are played around with by GM
by that I mean there is a + brown and a - brown and same for lt green

wrchism said:

If the factory head unit has speaker level outputs, what happens if you bypass the factory amp and let the factory head unit drive the speakers directly? ?Is the factory amp the weak link in terms of sound quality? ?Is there enough power in the factory head unit to do the job?

I was initially surprised to find that the Av had an additional factory amp . . . not that long ago, all factory head units drove speakers directly! ?Has anyone tried this?

Click to expand...

I doubt that you would be please letting the OEM amp drive the OEM speakers...Not sure why you would want to do this?

Capecruis8der,
Heck of a job tracking down the wires!!! I did this mod tonite, and MAN!!! did it make a difference taking the factory amp out of the eqation and letting my kenwood drive the speakers I can already tell I am going to have to replace the factory speakers with some much better ones, any way, great hack Capecruis8der!!!

Gatorjedi

I just did the factory amp bypass. I couldn`t get the top plug to come out though. I guess this is okay isn`t it. I haven`t had a chance to get to listen to it too much as it is raining and I just didn`t want to sit there.
Is it okay to leave the top plug plugged in?

The top plug is for power and amp turn on
don't see any great harm
just unused power drain

it is differcult to get to especially with big fingers
TRICK
used a piece of two way tape on the tip of my finger and stuck a 1/4" x 1/2"L hexcap bolt to it

It was just enough to get around back and push in plastic lock on plug---
use a small mirror to see around back so you know what to push

Thanks cruis8er, I will give it another try tomorrow.

Ok, I did it. The only thing is that I still have the factory speakers in and at low it sounds great. But when I turn up the volume it starts to get all distorted and sound like crap. I know I did everything correct.

Could it possibly be just that the speakers are crap?

Manny

SICILIANOSAVY said:

Ok, I did it. The only thing is that I still have the factory speakers in and at low it sounds great. ? But when I turn up the volume it starts to get all distorted and sound like crap. I know I did everything correct.

Could it possibly be just that the speakers are crap?

Click to expand...

I haven't done this mod since I have aftermarket amps but the OEM speakers leave a lot to be desired. You will notice a difference replacing the factory paper speakers.

I would also suggest to replace the speakers. Check out my pics to see the difference between the factory & an aftermarket pair.

Ok then here's my next ??, Are the front and rear speakers 6.5"? I have no clue as to their size.

Manny

SICILIANOSAVY said:

Ok then here's my next ??, Are the front and rear speakers 6.5"? I have no clue as to their size.

Click to expand...

Yep. 6.5" front & rear. The factory rears are 2-way speakers and the fronts are components. Take note of this. You need to replace the fronts with component speakers. In the rear you can pretty much install what you want.

Other thing to keep in mind when selecting your speakers in the mounting depth of the speaker. Make sure it fits our truck. Crutchfield has a good online guide for this.

Good Luck!

I will try this mod next weekend. Thanks for the tip.

Do you happen to know what the depth is?
Thanks guys. You guys are really great. I really appriciate the help and info.

Manny