P0340 at start-up, doesn't come back on while driving.

Shut the engine off.
Restart, P0340 comes on immediately.
Truck runs fine, erase the code, light stays off until shut off, comes back on at start-up again.

I have an all new ignition/control system 1.5 years ago; ECM, plugs, wires, distributor/cam sensor, cap, rotor, coil and module.
The distributor is a rebuilt AZ unit. I'm thinking therein lies the problem.

I checked the wire harnesses, no visible problems.
So, I'm thinking I'll pull the distributor out to replace the cam sensor (don't want to drop any tiny screws inside , plus it's hard to get at).

What say the experts.

P0340 is indicating there's a problem in the Camshaft Position Sensor circuit. Possibly, but not necessarily a CMP sensor, could be a loose connection, etc. The GM flow chart for diagnosing the DTC is quite involved. If AZ has been involved in the past, chances are pretty good it's the sensor ;)

Well, I replaced the pick-up coil (camshaft position sensor). Had to remove the dist. to do it, as I couldn't get the top plate to rotate/stop at the exact spot needed to wiggle the bugger out. Sometimes I admire Ford's front mounted distributors - today was one of those days. :rofl:

Put it back it, fire it up, 3 codes immediately.
The P0340 (active and stored), and the infamous P1345 (high voltage spike).

Erased them, truck idled fine, but drove like crap, bad missing. Turned it off, started back up and P1345 again. Now it starts hard; misfires, backfires, clunks. I dinked around with the cap and rotor, swapping out the 1.5 yr old units with an extra set I bought 1.5 years ago.
Still the P1345. Crap, I either jumped a timing chain, or inserted the dist. off a few degrees. It seemed to go back in about 5-10 degrees clockwise from where it came out, but if I backed off a tooth, it seemed to be off the same amount the opposite direction.

So, because I love doing things over, I took it out again.
Turned it 1 tooth to the left. Viola, no SES lights.
Drove it 5 miles. shut it off 3 times. refired 4 times, no SES lights.
This suprises me that the oil pump shaft lines up properly. The bottom of the dist shaft has a pin thru it that I think drives the oil pump. I wonder how it can let me put the distributor in off by however many degrees one tooth on the drive gear is. (guessing 20 teeth, 18 degrees a tooth)

I did notice the cheapo plastic distributor housing has a stripped mtg screw, so some day I'll have to get another distributor. Looks like Autozone parts are good up until the warranty ends (1 year on the dist. and it had a new sensor mounted in it, 2 years on the new sensor). Just waiting for the distributor to crap out now. 2 hours to fix it. Beeer time now.

For a truck with only 85k miles, I sure do have some rotten luck with it.
Let's see what pops up tomorrow.

Thanks for listening.

Guess I better cancel the appointment to fix my crystal ball, it seems to be working again...damn thing. P1345 pops up when the distributor is off a tooth or more, along with the backfire and no power. You've got it perfect now or the SES light would come on. The slot in the oil pump drive is wider than the pin in the distributor, plus it's a tapered opening so if you're close with the distributor, it'll turn the pump and fall in... the oil pump turns quite easily. Next time, before you pull the distributor, line up the rotor with the "6" on the distributor housing and make sure the damper marks are lined up on the timing cover, saves a little time and grief... go enjoy your beer, you deserve it ;)