2000 GP GTP Electrical problems

[jwardl]

Would someone who knows be so good as to explain where all (or as many as you know/are willing to explain) the main electrical grounds are on a 2000 GP GTP? I've got a bunch of accessories that all went out at once, and that's what I'm betting on. BTW: Checked the fuses (even under the hood) -- all good.

I have an Alldata subscription, but am no good at reading electrical diagrams.

If it helps, the accessories not working are: daytime running lights, power locks (though the relay under the dash clicks), radio (every aspect of it), lumbar adjustment, rear window defogger, and seat heater.

Everything else works fine, though I've had the infamous "rainwater onder the passenger floorboard" issue many times over (any grounds under there? My blower motor actually has rust on it). Auto AC is fine, as well as auto headlights, signal, parking, and dash lights, HUD, power seat, DIC, dome light, brake/backup lights, engine starting (still instantaneously after 5 years and 135000 miles, in fact) -- you name it.

Since all the accessories failed at once, simple logic says they must have a common problem, and I'm betting on a ground. If it helps, I first noticed one day when putting the car into park that the radio woud be "pulled down" (the display would temporarily fade), and it would turn off when shifting into park. This, I discovered, was due to the factory computer setup of auto-unlocking the doors when putting the gear selector into park. I disabled that and the problem went away, but the radio still continued to be a problem when going over bumps. The display and sound would dim, then return, then dim -- and finally faded away altogether. Also, the power locks tried to actuate (when I pressed the button or set the alarm), but seemed to lack sufficient power to trip completely. DRL faded away as well.

This originally happed in the summer of 2004. Last winter, on the coldest days, the radio display would return dimly, but no radio sound. Some current was still going to the radio, obviously, because the time was still correct, and the station buttons still held the correct frequencies. Also, the lumbar adjustment began working -- but only for a minute, then dead again (after warming up?). No such joy this winter, even with equivelent temps.

I've really got the feeling that this is something fairly simple -- a ground -- but finding it without any idea of where to look would be a fool's errand. So, again, can anyone point out WHERE and and all grounds are? In addition, what do they look like? I'm assuming a bunch of wires come together to a bolt, but will this always be at some otherwise blank spot, or might some grounds be located on an actual component -- like the blower motor? Any other ideas would be appreciated as well.

[BNaylor]

If you suspect grounding the best place to start is at the battery negative. From there all grounding terminates at the engine/transmission grounding stud which is located on the back of the engine (driver's, radiator side). There are also grounds located in the main engine compartment fuse box, the cabin fuse box and left side of the dashboard. In order to systematically check them you will need a GM Grand Prix service manual. All other reference sources are too generalized. Just about all of the ground wires are color coded black. All electrical components reference or require a ground in order for the circuits to work.

Also, your problem could be some component loading a respective circuit down or going South. About all you can do is visually inspect the grounds, make sure they are properly connected and tight. After that a wiring diagram and multimeter will probably be needed. With the proper documentation you should be able to troublesoot and see what is common to all the problems you are having.

I can't make any promises but I'll review the wiring diagrams and provide hopefully be able to provide a starting point.

BTW - Welcome to the forum.








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]

Those are all ignition controlled circuits (only have power when ignition switch is on). The radio clock and memory is a different circuit so that's why they are not messed up. Stick with checking the ignition controlled circuits to narrow your search. I would start with the ignition switch itself, then move on from there. Bob, are all those items controlled thru that module that leaves power on until you exit the vehicle? I don't think the DRL's are, so that may eliminate it as a culprit.

[BNaylor]

Originally Posted by richtazz

Those are all ignition controlled circuits (only have power when ignition switch is on). The radio clock and memory is a different circuit so that's why they are not messed up. Stick with checking the ignition controlled circuits to narrow your search. I would start with the ignition switch itself, then move on from there. Bob, are all those items controlled thru that module that leaves power on until you exit the vehicle? I don't think the DRL's are, so that may eliminate it as a culprit.

I'd go with your suggestion of looking at the secondary ignition circuits like IGN 2 and all accessories, etc. from the ignition switch on. Main Ignition is OK since engine starts and is running fine along with no other driveability problems. RAP (retained accessory power) is always involved in the accessories. With the power door locks acting up the BCM module could be suspect too or components associated with it like RAP and Theft Deterrent. Also, I wouldn't rule out the ignition switch assembly. They go bad on later model GPs too.










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.

[jwardl]

Originally Posted by richtazz

Those are all ignition controlled circuits (only have power when ignition switch is on). The radio clock and memory is a different circuit so that's why they are not messed up. Stick with checking the ignition controlled circuits to narrow your search. I would start with the ignition switch itself, then move on from there. Bob, are all those items controlled thru that module that leaves power on until you exit the vehicle? I don't think the DRL's are, so that may eliminate it as a culprit.

Mostly true, but the power locks and lumbar adjustment have nothing to do with the ignition. They work (or, SHOULD) irrespective of the switch position.

Does that help?

Thanks for any and all comment.

[richtazz]

I'm beginning to lean towards a BCM, ignition switch or battery problem since the affected accessories are both ignition controlled and "always live" circuits.

[DonSor]

Did you say you have the schematic diagram of your car? That's the best tool you have. In it will show what accessories share a common source (common fuse, common relay, common module and alike)

[BNaylor]

On the lumbar problem it may be unique to itself or maybe associated with the BCM module. Lumbar uses the same "hot at all times" 12v as the rest of the power seats. Do the other power seat functions work? Have you inspected the wiring under the seat. There are two Lumbar Adjuster Relays. All ground wiring is black for those circuits. The ground point for lumbar is Ground G200 located under the left side of the dash which happens to be about the same location as the BCM. Plus check the electrical connectors to the BCM. I'd check the grounds at the lumbar relays with an ohmmeter and go from there.










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.

[BNaylor]

Originally Posted by DonSor

Did you say you have the schematic diagram of your car? That's the best tool you have. In it will show what accessories share a common source (common fuse, common relay, common module and alike)

He says he does but doesn't like reading schematics.

Me, I'm just pulling all my data out of my rear end even though I have a GM Grand Prix service manual.









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.

[jwardl]

Originally Posted by bnaylor3400

He says he does but doesn't like reading schematics.

Me, I'm just pulling all my data out of my rear end even though I have a GM Grand Prix service manual.

No, no... it's not that I don't LIKE reading schematics, it's that I don't know HOW.

I don't have the actual service manual, either. I have access to Alldata. Some schematics are available there, but I've had little success in trying to understand them and find common grounds between accessories.

[jwardl]

Originally Posted by bnaylor3400

On the lumbar problem it may be unique to itself or maybe associated with the BCM module. Lumbar uses the same "hot at all times" 12v as the rest of the power seats. Do the other power seat functions work? Have you inspected the wiring under the seat. There are two Lumbar Adjuster Relays. All ground wiring is black for those circuits. The ground point for lumbar is Ground G200 located under the left side of the dash which happens to be about the same location as the BCM. Plus check the electrical connectors to the BCM. I'd check the grounds at the lumbar relays with an ohmmeter and go from there.

In all your responses you continue to mention the BCM. Are you leaning toward that, or am I reading too much into it?

[BNaylor]

Originally Posted by jwardl

No, no... it's not that I don't LIKE reading schematics, it's that I don't know HOW.

I don't have the actual service manual, either. I have access to Alldata. Some schematics are available there, but I've had little success in trying to understand them and find common grounds between accessories.

It's not a problem, so don't feel bad. We're here to help. Automotive wiring diagrams are the worst around even the GM service manuals. People that can read or understand them have trouble. Is there any specific area you need reviewed? The people that did GM's technical documentation are either geniuses or stonewall idiots. I haven't figured out which yet. How is your troubleshooting technique and use of a multimeter?








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.

[BNaylor]

Originally Posted by jwardl

In all your responses you continue to mention the BCM. Are you leaning toward that, or am I reading too much into it?

The reason we're mentioning the BCM is because it's the heart of the interior electrical whereas the PCM handles engine/drivetrain. You mentioned shift interlock problems (BTSI) and power door locks acting up. The problem is troubleshooting the BCM is very difficult. Plus it's expensive so it's important to make sure it is the problem. The GM dealers will hookup a Tech II scanner and read any DTC codes that may be stored and perform a diagnostic procedure in a manual. Even if you were to replace the BCM, it would need to go to the dealer where it will be programmed for your VIN and options. I'd hold off for now on the BCM.

Are these items not working: daytime running lights, power locks, radio, lumbar adjustment, rear window defogger, and seat heater. Have you checked the fuse or 12v for lumbar/seat heater? The best I can do is review the wiring diagrams and see what's common. It takes time to piece it together. Based on how your radio is working, I'd say there is a short and it just a matter of figuring out where. It could be as simple as a fuse, relay or wiring.








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.

[jwardl]

Originally Posted by bnaylor3400

It's not a problem, so don't feel bad. We're here to help. Automotive wiring diagrams are the worst around even the GM service manuals. People that can read or understand them have trouble. Is there any specific area you need reviewed? The people that did GM's technical documentation are either geniuses or stonewall idiots. I haven't figured out which yet. How is your troubleshooting technique and use of a multimeter?

I have a small digital autoranging multimeter, and understand it fairly well. I have no experience doing auto electrical troubleshooting, but am willing to learn to save myself the potentially enormous expense of having a shop do it.

[jwardl]

Originally Posted by bnaylor3400

You mentioned shift interlock problems (BTSI) and power door locks acting up.

Are these items not working: daytime running lights, power locks, radio, lumbar adjustment, rear window defogger, and seat heater. Have you checked the fuse or 12v for lumbar/seat heater? The best I can do is review the wiring diagrams and see what's common. It takes time to piece it together. Based on how your radio is working, I'd say there is a short and it just a matter of figuring out where. It could be as simple as a fuse, relay or wiring.

No shift interlock issue; was just saying that I originally discovered the problem when shifting into park because that would cause the doors to unlock, which pulled the radio down.

You're correct about which items are failing. I've checked ALL fuses (near the glove box as well as the fuse block under the hood -- unless there are others). Haven't checked power other than running a multimeter across the fuse contacts of some of the failing devices. Unfortunately, I don't remember the results. Can do it again tomorrow though if it might help.