I believe my ECM is going bad due to intermittent wait to start lights, and it will crank but not start until that light comes on, even though it should. I had a battery go bad under warranty this winter which killed both batteries and I had to jump start it a few times, which was probably the culprit. Grounds are good, ecm plug and vp44 plug are clean with no corrosion or pulled out wires. My question is that occasionally I will turn the key to start the truck, and I just get a click-it isn't the starter solenoid or contacts because I did those recently and it has done it with 2 different starters. Connections all look good in the PDC also. Is power to crank the starter run through the ECM, or separate? Wondering if I may have a key switch going bad. I have replaced relays for the starter in the PDC. Thanks

 

When you say the grounds are good. You check with a meter and any cable stiffness?
I know a buddy who spent $3000 on parts only to find a bad $20 ground cable.
I have fixed a few vehicles because the ground had a clean connection but the cable was rotten.

Good Luck!