If anybody is having the same issue with a 2500HD 8.1 and sees this, I will share my fix. I have a 2003 Sierra 2500HD 8.1 gasoline. I got the P0342 code a couple years ago, replaced the cam sensor, replaced the crankshaft sensor, had the wiring harness checked, replaced PCM and the code would always come back soon after the engine started. The engine had a hard start/long cranking and backfiring. Once the engine started it ran just fine though.
GM has stopped making certain parts for 2003 and the timing system is one of them so even finding the new cam sensor and harness was a pain. I ended up converting my timing system to the 2004+ setup. Everything is the same fit for the 2003. You will need a timing gear set for a 2004 (The new cam gear has a different design for the new sensor), timing cover for 2004(the new timing cover has a raised section to allow room for the taller sensor), camshaft positioning sensor for 2004(taller sensor), wiring harness pigtail for 2004 camshaft positioning sensor(to cut and splice with existing harness wires).
I bought a new water pump since I was removing the old one to remove the timing cover and installed that as well. Truck fires right up like brand new every time and code has been gone since. I spent about 500 on parts. The only thing I had to purchase from dealer was the timing cover which came with gasket and oil seal installed. Everything else was an OEM part from an auto parts store in my area. You will need a special harmonic damper puller as the standard 3 bolt puller will not work. You need the Lisle puller, part number 51450. Lisle also makes the damper installer tool as well. I used the rental from AutoZone which is not ideal on this truck as the Driving Nut is recessed because the Damper is not flat faced.
Took me an hour and a half and a lot of sweat and knuckle busting to install mine back on where I'm sure the lisle installer would have made the job much easier. I also baked my crankshaft timing gear in the oven at 350 degrees for 15-20 minutes right before installing it. This will make the gear expand and slip back over the crank all the way without having to be pressed on. Line up the keyway and slide the gear on, leave it alone for 30 minutes, let the gear cool down and it will shrink and pressure fit itself. Hope this helps someone
Friday, April 29th, 2016 AT 10:15 PM