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Pete, Auto Service Technician
Category: Chevy
Satisfied Customers: 28794
Experience:  14 years GM dealer Technician.
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Chevrolet Silverado 2500 HD: My 2003 Chevy Silverado 2500HD

Customer Question

My 2003 Chevy Silverado 2500HD (6 litre gas engine) won't shut off when I remove the key.
Last year, I ran into the the reduced engine power problem that so many people have had. I found three wires that were broken running to the throttle body. I soldered those back together and truck worked great all year. (great is a relative term - check engine light goes on for anything over 80km/hr, ABS light flashes on and off intermittently, airbag light is always on etc...)
Truck got snowed in this winter (over 500cm in New Brunswick this past winter). When I could finally get it out after a few months of sitting, the battery had died over winter. After boosting the truck it immediately started up in REP and shook like crazy.
I purchased a replacement pigtail connector for the throttle body control and crimped it on and a new battery.
This is my current re-occuring sequence for the truck.
1) I have been disconnecting my battery between truck attempts - as soon as the negative terminal starts to reconnect I can hear the throttle body moving and the fuse box making noise. I have narrowed the noise down to the PCM2 fuse. After tightening negative terminal, the sounds end.
2) Truck starts up fine. No REP. Drives great.
3) When I go to shut truck off there are two options.
a) remove keys and truck stays running indefinitely - pull fuel pump, or PCM 1 or PCM 2 fuse and truck shuts off - then it will start up again perfectly
b) turn truck off and it the engine bangs and rattles a few times and shakes hard before turning off - then I try to start it up and it goes to REP
Based on what I've researched this may be a ground cable situation. However, I've been un-able to locate these ground cables.
Submitted: 2 years ago.
Category: Chevy
Expert:  Pete replied 2 years ago.
My name is ***** ***** I am a professional here at Just Answer. I noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.
Looking at what is described here this sounds like either an electronic ignition switch at fault (which can be very common as it may not send the correct signals to turn off the vehicle intermittently) or the engine computer itself at fault keeping the fuel pump and ignition on causing this issue here.
I would have the signals from the electronic ignition switch tested to see if the switch is the cause here and if found to be the fault it will need replaced.If these are found o.k. then the signals from the PCM need checked to see if the PCM needs replaced.This is best tested with a multi meter.
Thanks Pete