The ground circuit appears to be closed with the key on, but when the engine is cranked, there is no power at the coil, so it makes me wonder if there is really a wiring problem after all.

The cam and crank sensors appear to be working and sending a signal. We think we have eliminated a bad PCM as a possibility. Yet somehow, the PCM appears to not be operating the ground during cranking. What the heck else could be going on?

 

No power at the coil while cranking implies the PCM is either bad, or not getting signal from the crank sensor. It has to see the engine turning to trip the ASD relay again, if it doesn't, you won't have power at the coil, or injectors, while cranking.

 

Maybe the replacement PCM I got was bad, too? It is curious that the original PCM threw a code for no power at the coil during cranking, while the remanufactured PCM never did that. I just dropped the remanufactured PCM in the mail yesterday to get a partial refund...maybe I should call them on Monday and ask them to please re-test it upon receiving it. I kind of wanted to hang onto it just in case, but I also didn't want to send back the original PCM, either because they said not returning the core would cost me an extra $100 and would also void the warranty on the reman'ed PCM.

Ugh. This is getting frustrating...

Thanks again for all of the input you've provided, Hey You. We'll keep at it. I may have to get it towed the the dealer soon.

 

Sorry to dig up an old thread, but I wanted to post an update in case anyone ever finds this thread in the future while trying to troubleshoot a similar issue. As it turns out, HeyYou was right all along (no surprise there!) in suspecting the PCM. After the previous mechanic finally threw in the towel after the replacement PCM didn't solve the problem, I had it towed to another shop. They did a lot of diagnostic work, and finally called and said that it had to be the PCM. They had monitored the crankshaft position sensor signal with an oscilloscope (I think?) and noticed that the 5V signal (again, I think that's correct?) was not a flat wave pattern (5V, then 0V, then 5V, then 0V, etc.), but was instead a series of peaks and gradual valleys. It appeared to them that the ground path for the crank sensor was screwed up, so they provided their own ground for the crank sensor and then the signal showed exactly as it should. However, the engine still failed to start.

So, I ordered a second replacement PCM and took it to them. They called the next day and gave me the good news that the truck started! They did find that the previous crank sensor (which was OEM and brand new, as it was the first thing I replaced when the truck died last June) was bad and had to put another one in. So, the only thing I can figure is that the first replacement PCM I ordered was faulty, or the original PCM failure kept frying crank sensors as the mechanic working on it at the time was fiddling with things, so when he plugged in the remanufactured PCM, the failed crank sensor prevented the truck from starting.

In any case, my truck is now back on the road. I hope this thread might help someone in the future. Thanks so much to HeyYou and everyone else that chimed in here to help me out - I really appreciate it! Now to troubleshoot the coolant leak on the passenger side of the engine, near the ignition coil....I'm fearing it's coming from the head gasket

 

Posting the fix, no matter how old the thread, is ALWAYS smiled upon.

Glad ya got it going.