Thread: '01 GTP - Electrical Gremlins [lights] troubleshooting?

Picked up an '01 GTP Sedan 150k mi, a few days ago, and having some trouble with electrical systems. Looks as though a previous owner did some shoddy electrical work, mainly audio, and trying to troubleshoot, looking for advice. Never messed with a vehicle that has a BCM. RAP, HUD, and DIC do work. Aftermarket radio was replaced with my own aftermarket head, using same 21-pin harness that I used on my old car, '00 Malibu.

1) fog lights won't come on - read they only activate with parking lights or lowbeam headlights engaged, and will kick off with the high beams engaged. Nothing. Switch, relay, or other likely culprit?

2) no interior domelights - Car has sunroof, and the two press-switch style reading lights in small upper console. Haven't checked bulbs yet.

3) no taglight - changed bulb, no dice. connections on socket themselves are clean.

4) DIC flickers - the left side of the DIC will flicker, and also echoes turn signals when they are on.

5) Blower Motor remains on with key off - figure a relay went out, and someone wired it direct. troubleshooting tips?

6) weak door chime - sounds muted/distorted. replaced rear speakers, front right works, front driver side does not.


That said, I friggin love this car. Never want to drive something without a HUD again!

Awesome, thanks for the tips.

Question, would I need to track down a stock radio? I've read something to the effect that removing it can screw all kinds of stuff up, and some installs just relocated it to the trunk to make onstar, etc, play nice.

I don't think it's a bose system, RPO codes on trunk sticker show -

UP3: AM/FM STEREO, SEEK/SCAN, COMPACT DISC
UW6: SPEAKER SYST, 6, DUAL F/D TWEET & WOOF, DUAL EXT

Forgot to mention, keyless entry fob does not work either. Have not ruled out damage to fob itself though.

I've seen [well, smelled] no obvious signs of water damage. Carpet is not discolored.

But, tomorrow I'll go by a parts store, have them test the batt & alternator, then progress from there.

Checking Grounds is the easy step 1. If all Grounds are good, things get.... fun...

First thing I would do is pull the halfassed work done to the wiring. Get the harness behind the dash as clean as possible. You don't have to get an OEM stereo, just undo all the crap for now. Cap the ends of all the wires you expose to prevent any crossing, aarcing etc.

Check for some of your issues. If they are gone, great, if not then further teardown is needed. Are the HUD and DIC factory options on your car? If yes, great, if no then you need to dig deeper and find any modifications to the wiring. This could involve literally pulling the entire dash out.

Also, not for nothing, check out the BCM. If something has happened to it, it could cause many of these issues.

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thanks all for the advice.

So, got the tag light working. Ended up being a bad connector, spliced in a new one, good to go. Connections soldered and wrapped in heat shrink. One gremlin down.

Did some poking around, found that the dome lights were non-functional due to the fuse being pulled. Replaced it and.... They won't turn off. Explains the pulled fuse, haha.

There is also an extra wire jumped into the interior fuse box, under the DRL fuse. Not sure where it leads, appears to go through door jamb to underhood area, then disappears into the factory split-loom, near the battery.

I'll poke around more this weekend when i have the time.

Originally Posted by nox

First thing I would do is pull the halfassed work done to the wiring. Get the harness behind the dash as clean as possible. You don't have to get an OEM stereo, just undo all the crap for now. Cap the ends of all the wires you expose to prevent any crossing, aarcing etc.

Do you know if the non-bose audio used a separate amplifier as well? From the bit I've looked around, there are some [4, looks like 2 conductor] extra wires leading from above the AC control panel to behind the glove box, i suspect it is wiring to bypass a stock amp.

Originally Posted by nox

Check for some of your issues. If they are gone, great, if not then further teardown is needed. Are the HUD and DIC factory options on your car? If yes, great, if no then you need to dig deeper and find any modifications to the wiring. This could involve literally pulling the entire dash out.

As far as I can tell, HUD and trip computer were standard on '01 GTPs. Found a pdf spec sheet from GM. What I'm calling the DIC is the little screen that indicates doors open, boost gauge, and will cycle through Fuel Used, Range, Oil Life, and MPGs. Is DIC or trip computer the correct term for this?

Originally Posted by nox

Also, not for nothing, check out the BCM. If something has happened to it, it could cause many of these issues.

How would I go about checking the BCM, or is that best left to a shop? Also, I'm assuming that's the box near the onstar unit in the trunk?

Still scratching my head about the blower motor running with key off though. Gut instinct tells me a relay was bypassed, and a constant hot was used rather than keyed.

Originally Posted by Gregorius

The biggest bummer on these, is that in order to even swap in a code matching Junkyard radio, they need to be "Programmed in" by the Dealer, or someone with a Tech 2. Anti-theft, VIN matching etc.

Yes, pain in the ass. Door chimes, Sat radio, a feed for HUD info all goes thru the stock... bastard of a radio. There are new "rebuilt" radios on ebay, they even come with an Aux in jack on the face-plate <Phone Jams!>. I don't remember if they need programmed in or not. Round 300 bucks though.

Chimes didn't use the radio until later I'm fairly certain. This car being an 01 had them handled separately. 05 I think is when chimes were integrated.



OP: I should clarify, are they the units from the car. If they are scrapyard pulls or used units something could be wrong with the install.

The wire in the DRL circuit sounds like someone wanted 12 Volt when the key was "on." This is often the case with dash cameras or other after market AV accessories.

Interior lights being "always on" screams a short in the system.

I am sorry to be rude, but severe electrical gremlins are on the edge of being outside DIY territory. If you have experience or a friend with experience you can really proceed, but if you are coming in totally blank a shop is recommended. Shorts can go as far as causing fire in the vehicle. Additionally, GM is obnoxious when it comes to swapping many components that are integrated into the system, offend requiring them to be programmed to VIN match the rest of the system or they will not function correctly.

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Are the HUD and DIC the units from the factory or are they swapped in replacements? Even if the car had OEM HUD and DIC if they got replaced and installed incorrectly it could cause issues.

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