ahhh mine was low/no input. I had seperation in the harness on the pass side. Not sure what is causing a high voltage problem. I would trace the CMP wires to the PCM make sure nothing is bare or touching metal...

 

There are no bare wires in between the CMP and the PCM........

 

You have checked every inch? No worn, cracked or melted wires? continuity checked with a meter?

 

I could not find any sign of wear, cracks etc anywhere, I am electronics ignorant and have no idea how to check continuity...

 

The mystery remains unsolved

 

In the factory manual under code P0343 there is a diagnostic procedure. What evil02z said is step number one. Did the dealership run thru the procedure, or what exactly did they do for $150? use a Ouija board? The procedure basically is to tell you whether you have a problem with the CPS, wiring, or PCM....if they did it CORRECTLY (<- key word here) and said the PCM is bad, you should replace it.

About the hard starting....the PCM will start the engine with no CPS by relying on the crankshaft position sensor, but has to guess whether the engine is on a compression or exhaust stroke until it gets it right. This is what causes the extra cranking. This is in the manual under p0343 also.

PRIOR to the problem, did you do any mods to the engine that might have involved working in the area of the CPS or wiring?

 

As far as the $150, all I got out of the tech was that I needed to replace the PCM per GM tech line. He didn't say what he tested or how he came to this conclusion. It doesn't seem likely to me the PCM could be bad just because of one sensor but I guess anything is possible....