2006 Cobalt SS S/C with a 2.0L Ecotec.
Bear with me, it is an absolute mess.
To start off, the car was throwing multiple codes, evap sensor replaced, O2 sensor replace as well.
-Still threw codes, followed wiring harness, found numerous wires that were shorted out (not receiving ~12volts).
-Soldered and wrapped new sections of wires to PCM. Still throwing codes.
-(Something happened, father is a mechanic, he found a loose wire to nowhere, closed circuit. Car went into I believe theft mode?)
-No dash lights (Check engine light, brake light, etc.) except for the security light coming on when I turn the key on attempt to start car, nothing happens. Security light then turns off
-Looked up how to do a security relearn. Attempted that. But the security light does not remain on, which leads me to believe problem is elsewhere. Maybe the PCM?
-Changed PCM to a ZZP 1.0 PCM.
-Car will still not turn over nor start, dash lights still out, minus the security light coming on only when key is turned on, goes off after a few seconds.
-I have checked fuses have yet to find any bad ones.
..
I am at wits end with this car, any advice on what to do would be greatly appreciated.

 

double check ecu connectors are on tight and the fuse block is screwed down tight, could also have a ground loose somewhere.

 

Checked both, able to bypass crank sensor and start the car, still no dash lights

 

Sorry to hijack post but I'm having similar issues. Dose any know where to buy a complete wiring harness? From PCM to all the sensors and connectors in engine.