Rebuilt engine and trans on my Neon and when I tried to start it did nothing, no noise nothing. I did some troubleshooting and found the ECM was died. Had 12volt to ECM but no volts to starter relay. Ordered a remaned/reprogrammed ECM and it started right up. I drove the car about 160miles and the ECM died again with the same fault, no crank and no power to starter relay. I'm guessing that I have a short in the engine wiring harness. Where should I start to look?

 

The wiring to and from the PCM? If you think you have a wiring short, you need to go over the wires; plain and simple.

 

Have you found the wiring problem yet? If not, I have had a very similar situation and I found the wiring insulation to be melted or worn going to the alternator and crankshaft position sensor. The wires run between the exhaust manifold and passenger side axle. I plan to go to a local u-pull-it yard and get a wiring harness (at least from the corner of valve cover to the ends) to extend these wires to run against the firewall away from heat and moving components a.k.a. axle. A question I have (if you or anyone else can answer) is did the ECM get destroyed or is there something I'm missing to get this engine cranking again without buying another ECM?