Thread: 2004 Grand Prix GT2 won't start (short circuit)

Hello!

I tried to start my 2004 Grand Prix GT2 after 11 day while I was travelling, but it would not crank. I could hear the starter unsuccessfully trying to start.

I figured my battery wasn't holding charge properly, so the first attempt was to charge with jumper cables to an SUV; and it wouldn't turn over. 2nd attempt was a small battery booster, again it wouldn't turn over. Three's a charm though, and the third try with a commercial-grade battery boost got my car running. This got me home from 250km away (4 hours later), through a gas station, picking packages up, and crossing the border without shutting my car off. All the way, at least a dozen times 'Charging System Failure' came up on my dash computer, especially when hitting high revs while passing other vehicles.

So I get into my driveway, shut the car off, and try to restart it... nothing. It won't crank again.

I don't think it's the alternator because I drove for 4 hours without issue.

I don't think it's the starter because the engine did crank with a commercial boost hooked up in parallel; it just took a lot more power to get it going (the external connection).

I removed corrosion from both terminals and re-seated the cables but this didn't seem to change anything.

I removed the negative battery clamp from the negative terminal, and with a multimeter was able to see a 12-14V difference between the two components. I also saw a voltage difference between the negative terminal and the engine... which leads me to believe the positive battery cable is shorting to the chassis somewhere. I removed fuses one by one from the engine compartment fuse block but I wasn't able to track the source of the short - this leads me to believe there are more than one shorts to the chassis, or that the short is off of the main positive terminal cables.

Are there any common points of failure on the 2004 Grand Prix for the battery cables? Is there an easier way to diagnose which component failed/where the short is?

I pulled all the fuses from the fuse box and put them back one by one. 4 of the fuses cause my multimeter to read 12V:

Fuse 26 (BATT MAIN 1 40A)
Fuse 27 (BATT MAIN 2 50A)
Fuse 30 (BATT MAIN 4 30A)
Fuse 16 (PCM/ETC 15A)

Pulled the starter out and bench tested it with jumpers, the bendix popped out and was fine. Anyone have any ideas?

When the starter was being powered off the wiring harness, there didn't seem to be enough power to get it to fire properly to start the engine, so we thought the starter might have gone bad. Pulled it out and bench tested it using jumper cables, and it ran properly. The bendix popped up and it spun up pretty fast. Looked at it carefully, didn't have any dead spots. So I think there's enough current leaking from somewhere that's causing the starter to not run when connected to the electrical system.

With respect to the fuses, what I was seeing was if any of the 3 MAIN BAT fuses were in, the 12V from engine to negative terminal was detectable. If those 3 fuses were removed, and the PCM/ETC fuse was in, then I could still measure 12V difference. Is there a way to find out what those 3 MAIN BAT are providing power for? I leafed through a few electrical diagrams in my Hanes manual but didn't see the fuses labelled properly.

Negative terminal to PCM (in the air cleaner housing) has 12V too...could be the PCM shorting out? Or it's registering that voltage due to the short to ground elsewhere. I'll try disconnecting the PCM cables tomorrow to see if the short persists.

I bet its one of your battery connections. the 04+ battery connections suck !

Unplugged the three connectors from the PCM, and the short persisted so I reconnected it. I disconnected the remote positive terminal, and the short disappeared. Re-connected it to continue plugging away.

Pulled all the fuses in the instrument panel fuse box, didn't make a difference.

Disconnected a lot of the under-the-hood connectors, but wasn't able to narrow it down. Starting to run out of ideas. There are a few more connectors that I want to try getting at from the underside tomorrow when I put the starter back in.

Could the fuse box be faulty somehow?

At a loss for words. Re-connected everything, and my car started up. Will check tomorrow if there's still a short, didn't get the chance since my neighbour who helped me put my starter back in hammered my negative terminal on pretty tight. Also hoping it starts tomorrow morning ran it for 20 minutes to make sure the battery charged.