will not crank at all

You may have a problem with the anti-theft system. If so there should be fault codes stored in the engine and body computers. Next time the problem occurs take note for the "theft" light, if there is a fault is should be flashing. This could be caused by a faulty key or the key senor in the steering column. A communication problem between the various computers could also cause this problem. The first step to try and find the cause would be to check all the computers for fault codes using a scan tool.

hey just had this problem on my 200 gmc denali. Its the starter. The connection in the inside is going. i re sodered the positive that goes to the key to the soder on the starter its self. clean this connection and your good to go. if you cant soder or dont want to mess with it buy a new starter but there 160 bucks.

HAD THE SAME PROBLEM PUT IN A STARTER PROBLEM CONTINUED IT WAS THE BATTERY CABLE CONNECTION TOOK THEM OFF AND CLEANED NO FURTHER PROBLEMS.GOOD LUCK

I had this problem. Does your dome light go out when you turn the key over? Check your connections really good on the battery, make sure everything is tight. Even take them off and clean them. My problem was my battery wasn't producing the cold crank amps for some reason. It would do it when it got really cold. But when I took it places to test it, it tested fine. I put a new battery in it and haven't had a problem since. So maybe try another battery? Use one from someone else's car if you dont want to buy one. Just make sure its big enough to crank the engine. If thats a no-go, try checking the starter connections, or even take it off and have it tested.