99 Grand Prix GT Radio problems

[richtazz]

I have a baffling problem with my sound siystem I hope you guys can help me on. My rear speakers work when they feel like it, and lately, my left front is cutting in and out as well. My significant other has a Trans Sport minivan with the same radio, and after switching out head units, the problem persists, so I believe that eliminates the radio as a culprit ( when my rear speakers quit I switched radios, mine works perfect in her van, hers still has no rear speaker output in my car) My car has the CD with EQ, but it's not the Bose system, and sounds quite nice when it's working properly. My car also has steering wheel controls and a Heads-up display, and I want to keep those features. Is there a known wiring problem with these cars, and if so, where is the problem???? Thanks in advance for any info.

[BNaylor]

Originally Posted by richtazz

I have a baffling problem with my sound siystem I hope you guys can help me on. My rear speakers work when they feel like it, and lately, my left front is cutting in and out as well. My significant other has a Trans Sport minivan with the same radio, and after switching out head units, the problem persists, so I believe that eliminates the radio as a culprit ( when my rear speakers quit I switched radios, mine works perfect in her van, hers still has no rear speaker output in my car) My car has the CD with EQ, but it's not the Bose system, and sounds quite nice when it's working properly. My car also has steering wheel controls and a Heads-up display, and I want to keep those features. Is there a known wiring problem with these cars, and if so, where is the problem???? Thanks in advance for any info.

What year was your GP Rich? I'll send you the wiring diagram.



Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[richtazz]

it's a 99, and thanks a bunch!

[BNaylor]

Originally Posted by richtazz

it's a 99, and thanks a bunch!

Not a problem Rich. I can email you the page in JPEG format from a 97 - 98 GP GM service manual. Its basically the same for '99. Just send me a PM email with your regular email address. Don't like posting stuff from the service manual in public unless I have to.




Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[richtazz]

I think I've seen this issue before, my rear speakers cut out when the outside temp drops below 84-85 degrees, above that temp, the right rear will come back first, then the left rear. It's truly bizarre, and it's making me crazy(er). Anyone ever hear of this and if so, what's the fix? The harness shows no signs of corrosion or melting.

[BNaylor]

Originally Posted by richtazz

I think I've seen this issue before, my rear speakers cut out when the outside temp drops below 84-85 degrees, above that temp, the right rear will come back first, then the left rear. It's truly bizarre, and it's making me crazy(er). Anyone ever hear of this and if so, what's the fix? The harness shows no signs of corrosion or melting.

Sounds like a problem I've had with my Sony home stereo system for the past few years. Got it troubleshot down to some output power transistors in the amplifier but no parts are available so I run it as is.

Rich, check with KustomKid54 (Jim). I believe that he had issues with the stereos on a 97 and 98 GP. Maybe something matching your symptoms. You'll probably have to send him a PM because he's been off the forum for a few weeks.





Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[richtazz]

thanks for the tip Bnaylor. I've tried swapping radios with a known good head unit, and it does the same thing(mine works perfect when installed in the other vehicle as well). According to the GM computer, when I put in my VIN, it doesn't show that my car has the additional low frequency amp, so I don't believe that is the problem either. So that's where I stand, as I said before, it's making me CRAZY(er)!!!

[BNaylor]

Originally Posted by richtazz

thanks for the tip Bnaylor. I've tried swapping radios with a known good head unit, and it does the same thing(mine works perfect when installed in the other vehicle as well). According to the GM computer, when I put in my VIN, it doesn't show that my car has the additional low frequency amp, so I don't believe that is the problem either. So that's where I stand, as I said before, it's making me CRAZY(er)!!!

Are you sure you don't have a low frequency amplifier? Normally, if you have the CD/Equalizer which is the "premium" sound system there should be a LFA. It should be under the passenger side of the dash. I reviewed the wiring diagram and since you've illiminated the head unit all thats there is wiring to the rear speakers or a LFA, if equipped. The other possibility is one of the rear speakers causing all problems. If one goes South it may be introducing an impedance mismatch which will be felt back to the output circuits of the head unit or LFA, if equipped.

I don't think that there is a fuseable link in the circuit or a temperature limiter. To me it sounds more like an electronic component such as an output power transistor acting up. When they act up like that its called clipping or saturation or it may not be biasing properly.

Let me know what you think.




Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[richtazz]

I'll have to tear the dash apart and see, because now that you mention it, I hooked up an aftermarket speaker and it played, but sounded tinny (no bass). Thanks again B.

[richtazz]

just for everyone's future reference, the problem was my rear speakers. The voice coils were shorting out, and working intermittently. Replaced them with aftermarket speakers and all is well. Another note, Best Buy sells the harness so you don't have to cut your factory harness for $6/pr.

[BNaylor]

Originally Posted by richtazz

just for everyone's future reference, the problem was my rear speakers. The voice coils were shorting out, and working intermittently. Replaced them with aftermarket speakers and all is well. Another note, Best Buy sells the harness so you don't have to cut your factory harness for $6/pr.

Glad you got it fixed and thanks for the feedback.







Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.