2006 Jetta: rough idle/vibration, code P0343

[mantsek]

I have a 2006 Jetta 2.5L, that's been acting crazy.
The P0343 (cam sensor high voltage) was on. The car wouldn't start. I have changed this in the past, and drove the car a about 100 miles, but the code came back. Then the mechanic replaced 2 bad ignition coils, and the car run fine again for a few miles but the P0343 code stayed on. After a few miles, it started idling & shaking very badly, and then the engine will shut off. I replaced cam sensor (the 1st one was new too), cleared code and car was perfect for a few miles, then the code came back after about 15 miles. Car still drives fine after 30 miles, no rough idling, but I fear the shaking/idling will start again, since the code is back. So now I don't think its a defective sensor. There is probably another problem. Someone suggested it is a short in the wiring harness- how do I check that?
Any help will be greatly appreciated. The car is out of warranty.