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Need Help This one Pulls My Teeth

T

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Hi I have a 1999 GMC 3500 6.5 diesel the truck has a unique problem It wont shut off. I have replaced the ignition switch with the same results, I am able to access the fuel solenoid via the scan tool and shut it down. can someone assist me in this regard it would be greatly appreciated.:mad2:
 
You have a wiring problem. There are two things that should shut off your truck. One is the Computer first and foremost. With Ignition off the computer turns off, so your ignition is not working correctly. Second is the ignition provides battery voltage to both the PMD and the Fuel Shutoff Solenoid. Both of those must have power for the truck to run. Your ignition switch is not working correctly. You or someone hot wired battery voltage to ignition switch power somewhere. Maybe you or someone installed an accessory and tied a line from the battery to an ignition wire.
 
The fuel shut off solenoid isn't what actually shuts the engine down. The ecm is SUPPOSED to shut the fuel solenoid down. I'd look for a comunication problem from the ignition switch to the ecm.The fuel SHUT-OFF solenoid should kill it even if the main fuel solenoid doesn't. It's a built in redundant system. Perhaps the SHUT-OFF solenoid has been gutted[plunger removed or not functioning]
 
Thanks a lot buddy i just ordered a new ignition switch maybe i got a lemon b4 there is no history of the ignition being jump tho
 
Thanks bk95td for your info i am hoping that its not the ecm i contemplated that. I'm going to change the ignition again first with my fingers crossed
 
With ignition off, before cranking see if radio works, or interior lights. This tells you the battery voltage is shorted to ignition line somewhere, could be the switch, or wired it backwards. It cant be the PCM, it has to be the power to the PCM. The PCM has a direct battery source, but only turns on with the ignition power source.
 
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