My wife was driving to work this morning in her 04 GT (stock) and she said she hit a reasonably large pothole on the highway, and subsequently the entire car just shutdown (no power at all to any electrical system / motor). She luckily was able to pull off the highway unscathed. She turned the key to off, and then back to on and it fired up and carried on as normal. It made the trip back home this evening without incident.

I'm stumped as to what it would be. I checked the battery cables and they're solidly and cleanly attached. Besides, if the battery connection was momentarily interrupted by a bump on a loose cable, wouldn't the power cut out and then come back on right away? She said all the systems went completely dead....no gauges, no lights, nothing.

With the key in the ON position, I shook and jiggled even wire harness under the hood that I could find, but nothing caused any sort of power outage.

I'm wondering if it isn't something to do with the ignition switch. Has anyone had any experience with a faulty switch that would shutdown the car, or if not, does anyone think this is a plausible suspect?

I was also wondering if there could be a malfunction of the anti-theft system. I honestly don't know to what extent it works, but I didn't think that it had the capacity to outright disable the car (or does it?).

The other thing I'm considering is that the key wasn't properly in the ON position. If you tweak the key slightly toward the ACC position, it still is in "ON", but a gentle tug downward on a keyring moves it to an in-between position that is neither "ON" nor "ACC". And, of course, the power is cut to all the systems. Sometimes she has a "little" wallet hanging from her keys, which if it bounced up and down due to a big bump, could jar the key to this weird position. That being said, she is adamant that she didn't have her wallet hanging off of her key ring.


EDIT:

After talking to my wife in greater detail, I'm even more confused. She said that after the car shutdown and she coasted to a stop, she tried to put the hazard blinkers on (with the key still in the ON position), but they didn't work. In fact nothing worked. This is strange, because certain functions (hazard blinkers, brake lights, etc) should function independent of the key position.

After she switched the key to off, and then back to on, everything worked again.

So, apparently the position of key had something to do with "fixing" the problem, but it fixed problems with items that should function regardless of the key's position.

?????

I'm thinking ignition switch or maybe computer malfunction. But I'm really just stumped.


Also, she said it happened once before a couple of months ago, but it was at low speed at a red light, so it wasn't nearly as terrifying.

-- Wed Feb 01, 2012 11:55 pm --

Upon scanning the internet, this appears to have happened to many people, although it usually rears its head early in the car's life, not after 8 years and 90K miles. I'm not sure that anyone really found out the answer. Some reported new ignition switches, others new PCMs or BCMs. Sometimes, these didn't work. There is a TSB about the negative battery cable mount to the frame rail. Apparently cleaning it and using dielectric grease fixes some issues, but I don't know if it's relevant here.

No responses yet.....I may be SOL.

I honestly got nothing other than checking the negative cable to body ground. First time I've ever heard of this happening so I'm clueless, sorry.

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Dubs:00 VW GTI VR6, Low and Slow 91 VW GTI 8v, Shave the Bay!! 91 VW Cabriolet 8v, bitch Basket
GP's:04 GP GT, Past now G-Ma's Girlfriend's 97 GP GT, "Project Pink Power"

Of cases of this I found out there on the internet (reports to the NHTSA mostly), there didn't appear to be any certain fix. Dealership service departments usually replaced the ignition switch, the BCM, or a relay (basically throwing parts at it until it fixed it or the customer gave up and went home). I found on an Impala board that someone had found cracked solder points on BCM boards (probably where the connector is attached to the BCM).

I'm leaning towards a bad ignition switch, BCM, or PCM, or maybe the wire harness/connectors to the BCM or PCM. If I'm to believe the hitting the pothole and the shutdown are connected (and not just coincidence, which isn't impossible), it sounds like some sort of electrical connection was lost due to the jarring from the pothole, and that cause a total system shutdown (and all systems were offline until the ignition was cycled off and back on). Based on that hypothesis, I'll probably tinker with the BCM wire harness (move it around) to see if it disrupts the power. And of course, I'll check the battery negative ground, since it's a cheap no-brainer.

It's just weird that everything died. I can't help but believe that whatever happened to initiate the issue caused the computer(s) to crash to the point of nothing working.


Here's a case I found online: http://www.arfc.org/complaints/2004/pontiac/grand_prix/10145430.aspx

It seems that in that case the ignition switch was replaced. There is no indication in that report that the new switch resolved the problem or not.

-- Sat Feb 04, 2012 12:25 am --

Some more reports:

http://www.aboutautomobile.com/Complaint/2004/Pontiac/Grand+Prix/10126764

http://www.aboutautomobile.com/Complaint/2004/Pontiac/Grand+Prix/10123747

http://www.aboutautomobile.com/Complaint/2004/Pontiac/Grand+Prix/10102944

Well, I have no idea what the deal is with this. I'm giving up and taking it to the dealer. I'm OK working on easy-to-moderate mechanical issues myself, but this is out of my league, I'm afraid. I'll likey just get it back with no resolution, but I can't do nothing.

Diagnosing intermittent stuff like this is always a pain in the ass, so I totally don't blame you for wanting to take it into the dealer. Should help with overall costs too since you wouldn't have to try 4 different options before finding what was really wrong (because naturally automotive work never let's you get it right the first time haha.)
Keep us posted and sorry I was zero help at all with this. I'm still sitting here scratching my head.

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Dubs:00 VW GTI VR6, Low and Slow 91 VW GTI 8v, Shave the Bay!! 91 VW Cabriolet 8v, bitch Basket
GP's:04 GP GT, Past now G-Ma's Girlfriend's 97 GP GT, "Project Pink Power"

Talking to the service manager on the phone, he said he had no real clue what the problem was, and he had never heard of such a case in his experience. The only thing that came to his mind was exactly the same thing I first considered: loose battery cable. He probably thought I was just one of the uninformed masses, but I disappointingly informed him that I had already thought of that. I asked if a faulty BCM might be suspect, and he said that would throw an error code; somehow, I'm not sure that must be true.

Anyway, I'm taking it in later this week. I'll update the thread when I find out what it is (translation: when they give it back to me saying "could not duplicate problem".)

Intermittent Conditions Document ID: 964504
Diagnostic System Check - Engine Electrical Document ID: 910139
Ignition and Start Switch Replacement Document ID: 924620
http://sm.gpona.com:9001/si/numberSearchLink.do

-- Mon Feb 06, 2012 10:40 pm --

Testing for Intermittent Conditions and Poor Connections Document ID: 1762139

-- Mon Feb 06, 2012 10:45 pm --

after reading i think its the vehicle theft deterrent system, as it has a bug in it which kills all the lights when activated, which would kill the motor and everything till the password was inputted again aka key turned

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The anti-theft system definitely came to my mind, but I wasn't sure if it would kill all the systems or just the fuel pump/starter to prevent someone trying to start it without the proper PassKey to match the car.

If this could be the problem, could it be a malfunction of the ignition switch (i.e. losing connection with the key), or possibly even a bad key?

I did deactivate the anti-theft system in the DIC, but I think that might only disable the alarm and not necessarily the PassKey system.

Again, this is all stuff that I have very little knowledge of or experience with.

the passkey system will always remain active unless you manually bypass it and the bcm/pcm

it could be a random wire in the ignition so the car hits a bump, something happens, no password for pcm, fuel pumnp disengage which also thanks to the bug kills the lights and interior depending the year

but it was only vague references in the VTD system for 04 and in the main repair page not an update

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Well, here's the (lame) verdict from dealer service dept:

corroded battery terminal.

Right. In all fairness, I'm sure that it could be many things, most of which are difficult to detect. But I'm just not buying that a poor battery connection (and the terminal wasn't badly corroded at all in my opinion) caused the problem. An intermittent loss of battery connection, with the key in the ON position, should cause a "blink out" of power, not total shutdown with no return to power. It's simple to test. With the key in the ON position, loosen the negative cable and disconnect it. Then touch it back to the battery. Everything electrical that was on comes back on. That isn't what happened in the incident with this car. In this incident, the key had to be turned to OFF, then back to ON. This to me indicates a "crash" of the computer control system(s), or a failure of the ignition switch. Even if the "corrosion" simply caused a drop in voltage, I still don't think that explains what happened.

As always, I'm left feeling that my opinion has been totally dismissed by the service manager.