I hooked my 1997 sierra up to a OBD Scanner and it reads that i have a P1345 code which is a camshaft to crankshaft correlation fault. Could it be a bad sensor or is it automatically my timing change that needs to be replaced?
You are correct, the ECM has detected the timing from the crankshaft and camshaft is off to far to set off the DTC code P1345. It's more common for distributor gear to be worn then your timming chain. If your timming chain is stretched, you can hear it rattleing under hard acceleration.
The 1996 and newer Vortec is a non adjustable timing. There is a very good chance that replacing cam position or crankshaft position sensor will not fix this problem. This code tells you that the base timing of the vehicle is not correct. You really need to get the vehicle scanned with a scantool that will read the cam retard with the engine running over 1200 rpms and then make adjustments by turning the distributor, unless it is timing chain/gear stretch/wear or wear on the distributor gear. You could mark the current distributor orientation and turn the distributor counterclockwise, clear the code and start the vehicle and rev over 1200 rpm to see if it comes back, but the scan tool that can read the cam retard is the best way.
FYI The cam position sensor is in the distributor and the crankshaft position sensor is mounted to the bottom of the motor near the balancer. But i would look in to repalceing the worm gear at the bottom of the distributor shaft, the 97 and 98s, Vortec engine is that the gears were soft and they would actualy wear enough to through off the timing and you could try to adjust the timing but at some point you'll run out of adjustment. Also, the real big problem is that the gear is also hooked to the oil pump and at 75 or so, it may strat to mis-fire and backfire because the timing is so far off and the oil pump is also run off the same gear and your oil pump can fail.
This is a common problem with that vintage of GM distributors because you could usually adjust the timing enough to get the code to go away but you are just masking the real problem. Friend is a GM certified Tech, worked at an Olds dealer for 10 years before opening his own place, but he had never herd of this as being common. He then proceeded to show me a box with about 25 to 30 gears all worn the same way and all from 96 thruogh 99s that had SES lights on. And now with a $40 part and less than two hours labor and ten minutes on a scanner all these 100K mile trucks run fine and can pass E-Test.
Good luck and you really need a Tech2 scanner to get a better picture on why your getting a P1345 DTC code, but most likely it's going to be a $40.00 distributor gear.
