GMC Troubleshooting Questions? Ask a Mechanic for Answers
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.
On this model the BCM has to be replaced with a new replacement then programmed to your vehicle as a used BCM is already locked to one vehicle and cannot be reprogrammed to operate in your vehicle here.
One component I have seen cause this issue intermittently like this can be the electronic ignition switch itself not sending the correct voltage signals when cranking the engine.If you have not had this switch tested this should be done and if found to be the cause of the fault here it will need replaced.It is possible the BCM is the cause here but I would have the ignition switch tested to see if it is faulty at all.
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O.k.,since it did start up after being pushed into a warm shop and this does sound electrical here and the starter was already replaced and we can assume that none of the interior components like the BCM is the cause here since you tried to heat them up this may be the starter relay itself at fault.This relay is located under hood near the battery as seen in the link below.Try tapping on this relay when the fault occurs and see if the engine starts then or warm up this relay.If it does start then,this relay needs replaced.
If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.Thanks Pete.
Was this the same part number relay you swapped over as some relays actuate differently?
No this would be a square type relay box when pulled out it will have 4 prongs on it usually.Keep in mind which direction you remove it from so you can reinstall it the same way.
Try tapping on this relay while someone cranks over the engine and see if the vehicle starts and runs then.If it does then this relay needs replaced.
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I apologize for the delay.
Did the relay click at all when someone tried to crank over the engine when it wouldn't start?It should be heard or felt to click when someone is trying to start the engine.
Let me know,thanks Pete.