dtc p0343

[05silverado]

hello, i have a 2005 silverado 4.8l with about 73k on it. bought it new. well maintained by me. no probs until now. it threw a p0343 cam sensor high input code the other day. put a new one in and same prob. checked connector and wiring, all seems fine. the original one had oil on it below the o-ring. not sure if supposed to or not. also, i unplugged it and started the motor just to see what would happen and it threw a low input sensor code. plugged it back in and ran it and it threw the p0343 again. tach works. sometimes it has a hard time starting and backfires (i believe this is because the cam sensor only reads every other round and the engine doesnt know where it stopped so when it fires back up it has a 50/50 shot of getting the timing right). other than that, runs good and seems ok. i gotta get this thing smogged asap and cant until this is resolved. i did some searching for info with no luck. any input would be great - thanks.

[05silverado]

alright, i found the problem! after checking out all the wiring, connections, fuses, etc. i figured it had to be a mechanical issue. so i started tearing into the front of the motor. finally got to the timing chain front cover, pulled it off, and i couldn't believe it but the 3 cam spocket bolts were totally loose. i took them off with my fingers. this caused the camshaft to shift backwards in the engine causing the cam sensor to miss the reluctor wheel (it is very narrow) causing a high input code. 30 seconds at the factory and a few drops of loctite would have saved me hours of diag/repair. anyways, cleaned up the bolts and threads and reinstalled them with some loctite and torqued them to spec. put everything back together and problem solved. if you ever get a p0343 code and you have a LS-based motor with a 3 bolt cam spocket, park the vehicle asap before you cause any damage. chances are this is the prob.

[konigandy6]

Wow... thanks for sharing the solution. I was really racking my brain about your issue and couldn't come up with anything that made sense, especially since you replaced the sensor.

I'm glad you found the problem and were able to fix it.