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Pete
Pete, GMC Mechanic
Category: GMC
Satisfied Customers: 28772
Experience:  GM training and dealer tech for 14+ years. Diagnostics
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I have a 2000 Yukon Denali. Last winter the car began to not

Customer Question

I have a 2000 Yukon Denali. Last winter the car began to not turn over when the temp got below 15 degrees. All the lights etc would work. Push it into the garage and heat it up and the car would turn over and fire right up. Recently (Now Summer), it started to act the same way. Full power but would not turn over. I installed a new battery and starter and still no turning over. After letting it sit for a few days it fired right up??? Worked for a week or so. Let the car sit over night and again no start not turning over. So this time I replaced the BCM, the battery cables, the ground cables from firewall to frame, and the relay fuses---still will not turn over! I'm lost---any suggestions? The BCM was out of a 30k mile truck and tested at salvage yard before I purchased so I know it is good.
Submitted: 2 years ago.
Category: GMC
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.

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.

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.Thanks Pete.

Customer: replied 2 years ago.
Pete. Thank you for the response. So here's the kicker about this issue that confuses me the most. I undestand the BCM issue and switched back to original. Tried a new ignition switch and problem still existed.Now the confusion. Last winter I experienced this issue when ever the temperature went below 20 degrees. As soon as it warmed up outside the truck would turn over with no issues. The latest round with the no crank started when we had a fall cold spell but this time the truck won't crank even when Temps were around 60 degrees. Two days ago the temp came back up to 80 degrees and the truck started working perfect again.What is causing this issue that would be temperature sensitive? It's obviously in the starting circuit but I've heard of Temps effecting electronics. I'm lost. Any thoughts?
Customer: replied 2 years ago.
last winter I tried to rule out the BCM by putting a heater in the interior when the Temp effected the no crank. It had no effect! If I pushed it in the shop and cranked the heat to 60 the truck would start within 30.minutes of being in the warm climate. Spring came so I never thought about it again till now. Also over the summer I changed the plastic intake manifold out but did not change the temp sensor. Could that be an issue. Never heard of it being linked to starter circuit but could it send a signal to BCM?
Expert:  Pete replied 2 years ago.

Your welcome

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.

Customer: replied 2 years ago.
Again. Appreciate the response. So with the relay what I did during this last round is switch the 40 amp relay with the one from the heated seats. I only visually inspected the relays and neither appeared burnt. The switch made no difference. Thoughts?
Expert:  Pete replied 2 years ago.

Was this the same part number relay you swapped over as some relays actuate differently?

Customer: replied 2 years ago.
Good point. I just assumed all 40 amp relays are the same since you buy a universal one at part stores. Are we talking about the same part? I'm thinking the large fuse
Expert:  Pete replied 2 years ago.

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.

Thanks Pete

Expert:  Pete replied 2 years ago.

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.

Thanks Pete

Customer: replied 2 years ago.
OK. The truck is working right now but it's suppose to cool off again next week. In the meantime I'll buy a replacement and be prepared but will test per your instructions before replacingThanks again for your support
Expert:  Pete replied 2 years ago.

Your welcome.Let me know if you need anything else here and feel free to rate my help if you like.

Thanks Pete

Customer: replied 2 years ago.
Pete. Changed the relay and still no success. Any other thoughts?
Customer: replied 2 years ago.
An in addition the truck started fine last nite when I returned from travel. Temp was low 70s. This morning Temps were high 60s but it rained hard last night. Again no crank no start. I tapped relay and no luck. Went and purchased new relay and still no crank no start.
Expert:  Pete replied 2 years ago.

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.