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Old 05-11-2016, 05:54 PM   #1
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Default short causes loss of all power

I have an '01 Pont Grand Prix GT; I bought it new; all original. I have an intermittent problem. Sometimes when I try to start it I get power when I turn the ignition on; however, when I try to crank the motor, all power dies and the key is stuck in the ignition. I can disconnect the battery negative, reconnect it, and normally it will then start. I can also hook up a battery charger or jumper cables to it, then disconnect it, and the vehicle will normally start. Apparently, just supplying more volts seems to jump the short and it will start.
Lately, my tricks of disconnecting the battery is not working. I will get power back, but it shorts again when trying to crank the motor; or it will short out just after I reconnect the negative battery cable.
I took the vehicle to a mechanic. He suspected the body control module (BCM). He told me the BCM has a battery back-up and it should leave a code. Well, he checked and I have no stored codes.
Does anyone have experience with this short? I would hate to pay hundreds of dollars replacing various computers without a good guess of what could be shorting.
Thank you in advance for any advice you can give.
Brian
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Old 05-12-2016, 12:41 AM   #2
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You have an open, not a short....

Does your car have PassLock or PassKey Security system? Check owner'* manual.....

When car won't crank.......check all fuses for power......if you find a series of fuses, with no power and the key on, then you have a possible ignition switch problem....

Are you saying, you can rotate the key to on or crank, but you can't rotate it to the off position to remove?
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Old 05-12-2016, 11:42 AM   #3
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Thanks for the reply Tech II!
Yes, I have PASS-Key III security.
I'll check fuses next time it acts up, but I haven't checked them before. As I said, ALL power goes out.
You are correct on the key. It is locked in the "on" position. I can move it to crank; however, I can not move the key to the "off" position - it is somehow locked. I'm thinking I could use the manual switch to turn it off, but I have never used it before. It'* normally at my house, so I don't worry about it. I'll hook power to the battery and normally it will crank. This last time though I had to reconnect the battery about 6 times. Each time I connected it the power would come back for a few seconds, or until I try to crank the engine, and then I would lose all power again. I just let it set for a few days this last time and now it'* working again.
Would a faulty ignition switch be able to kill all power (interior lights, dash lights, exterior lights)?
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Old 05-12-2016, 12:16 PM   #4
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OK, so we have PK III...transponder in the key head.....when you just turn the key to "on"(not crank), does the SECURITY light go out after 3 seconds?

If you can't remove the key, then your battery can die/get weak....

If the key is in the steering column, as opposed to being in the dash, look under the column, in the key area.....you will find a removeable tab...remove it.......now stick a small screw driver upward in the opening.....you will be pushing upward on a plunger.....when you move the plunger upward, you should now be able to remove the key.......your battery may need charging.....when you turn the key to crank, it kills whatever juice is left in the battery......so check the state of the battery....a fully charged battery should register 12.6 volts, on a voltmeter.....If you turn the key to the crank position, and voltage drops below 9.6 volts(voltage needed to operate PCM), you battery is weak, and won't crank the vehicle......I think that is your problem, since you couldn't remove your key.... this is killing/weakening your battery.....

What I have seen cause this, is the wire harness going to the BTSI solenoid in the shifter......that harness flexes a lot.....one of the wires in the lock solenoid circuit, could be broken INSIDE THE INSULATION.....if it is, it can cause an intermittent contact, so sometimes the key can come out.....if the wire completely breaks, including insulation, then it will never come out.....some of those other wires are the circuit to the BTSI solenoid itself, and can prevent you from shifting out of park when the car is started....

So, see if you can remove the key by the method I showed.....then charge the battery good, with a charger.....

Then try and start the car....if it starts ok, shut it off and remove the key with the little screw driver......keep the screwdriver in the car....if you have no problems for a few days, I can almost guarantee the problem is the harness to the BTSI solenoid in the shifter.......to repair that wire, the shifter handle has to come off(pry out U-clip), and the top of the console has to come off to get to the wire harness for repair.....

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Old 05-12-2016, 04:18 PM   #5
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Tech II - Yes, the security light goes out.
I have a newer battery, and load tested it with a voltmeter. It drops to the 11v range, so I know it'* good.
My key release is to the right of the center console shift lever. I've never popped the protective cover or used it. I feel confident it would remove the key though.
What is the BTSI? If there is a short in the harness, I wouldn't expect it to kill all power to the vehicle. Is that possible?
As luck would have it - it never acts up when I'm looking to troubleshoot it. I guess my first step is to check the fuses and see if I have voltage going to any of them when I loose power. If I do not have voltage there, where would be the next place to check? I'm just not sure what could cause all power to cut out. I'm not sure where the battery positive lead goes on this vehicle. I'm guessing the main lead goes to the starter/solenoid, but I don't know where else it travels that could cut all power...
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