2005 GMC Yukon Denali will not start

leonb53

While going down the road the engine stalled and would crank but not restart.
I had the car towed to a repair shop where after a week and a half they determined that the ECM was bad and replaced it.
It worked fine for about a week and then started doing the same thing.
When I turn the key to the run position none of the gages operate. When I turn the key to start from there the engine cranks but does not start.
After I release the key and try to start again the is no cranking, or any other noise.
Trying again a few minutes later it cranks but does not start.
After removing and reinserting the key and turning it to the run position the gauges come up and then the car starts.
Back at the repair shop no one seems to be able to find the problem, and they have been testing for the past two days.
I would appreciate any suggestions

imidazol97

Just from past experiences and realizing I'm not an expert on the wiring layout of the Yukon, I'd be looking at the contacts from the battery to the positive connections along with the connection to the grounds. It acts in a way that could be from a corroded connection. On H-bodies, some of the positive cables are layered with a lead piece in between to give the top ones contact. Get corrosion inside that group, which is covered by a plastic cover, and strange things happen. Gotta pull back that cover looking for corrosion. The lead spacer is replaceable if you have one and it's been crushed.

But next I'd check the ignition switch. The cooling effect could be that you've got a corroded/burned contact inside which heats up, moving the parts due to expansion of the plastic, and breaks contact. That's the actual switch that has the contacts not the key lock cylinder I'm talking about. The clue here is that the contact for the starter relay and the contact for the power to the ignition system are two different pieces: one may be in contact as things shrink and cool while the other is not in contact. Therefore you can crank but have no power to the ignition. The shop should be able to verify that if it occurs for them long enough to test.

Second, would be checking the contacts on multiconnectors that are near the ignition switch looking for a burned contact or plastic around the contacts that shows heating damage. Then the plastic doesn't hold the metal contacts in the correct position. You might also check for a contact that has backed out a little bit--the metal tang that locks when the contact is pushed in may not have caught in the plastic hole for it and the metal contact is making a poor connection.

Good luck.

leonb53

Thanks for your help. I will let you know what is found

leonb53

The problem is solved.
There is a relay that when energized gives power to the fuel injectors. The relay went bad was replaced and so far so good.