Just got to the point where I could start my 01' 5.3l. In a 56 GMC with aftermarket harness and a reflashed ECM for street rod use. The fuel pump fires up with switched power but during cranking I can't get either an injector pulse with a noid light or a coil to fire to the plug wire. Both injector and coil wiring has power. Not sure what the OHMS are supposed to be on the crank sensor but it matched a brand new one out of the box so it should be fine, and it also has the 12v signal like it should. Checked the power and ground conncections at the ECM wiring and it's good. What am I missing?

 

You have to have some open ground wires somewhere in the harness undone. There should be a few.

 

System hot in BOTH crank and run key positions??
Ko and the system checks OK. FP primes as it should.
Try the same tests while the key is in the start position, and report back.

 

Don't have a switch yet, just holding the pink wire and the solenoid wire to the battery to see if it will start. Done this in the past with an LT1 and my brother in laws LS7 and it worked to fire up the engine. I do have 12v at the coils, the injectors, and the crank sensor, and swapped in another crank sensor and no change. The plugs for the PCM show to have good power and ground (I went by a pinout chart) The check engine light comes on as it should. I don't have the brake switch wire hooked up but shouldn't need it just to start. The fuel pump does come on for a couple seconds. I've heard that if it were a VATS problem it should at least try to start, then die. Not sure about the tune but I don't know anyone with a 99-02 5.3 truck that I could try the ECM in. Probably need a scanner but don't know which one would do any good. Don't want to waste money on a bad scan tool.

 

Just borrowed an AutoXRay scanner and worse news -- "vehicle not communicating with scanner." I double checked all my battery and ignition power wires in the ECM plugs and all the ecm ground wires and they are all good, plus I checked for continuity between the serial data wire and the aldl connector and it's good as well. I can't think of any reason why this thing won't fire or talk to a scanner other than a bad ECM. Is that right?

 

Bad PCMs are rare. Check the ALDL for the following.

 

4 and 5 both had a good ground, 16 had 12.4 volts, and the last wire had continuity from the ecm plug to the aldl

 

Sent my ECM off to the guy who sold it to / programmed it for me. He said there was a catastrophic failure. It wouldn't talk to the software in his laptop either. Asked me if I rewired the harness myself and I told him no, I used a harness from a guy in Texas who goes by techrods on ebay. The ecm guy says they are good harnesses, he was afraid I did it myself and crossed some wires. Anyhow, he's setting up a new computer and shipping it to me under the 1 year warranty so if I'm lucky I may still be able to hear this thing run this week!