OBD II P1345 Code on 1998 Chevrolet Blazer 4.3L V6 (Vortex) - How to Fix Camshaft & Crankshaft Position Correlation

P1345 - Camshaft Position Sensor Circuit Malfunction / Crankshaft-Camshaft Correlation. Check that both the crankshaft and camshaft are properly aligned at TDC. Also consider replacing the camshaft position sensor if it's faulty.

I replaced the camshaft sensor with a new one. I believe the cam and crankshafts are in the correct positions. After removing the timing cover, I rotated the engine until all three sprockets (crank, cam, oil pump) aligned as shown in my Chilton's manual — they were properly aligned at TDC for cylinder #4 compression stroke.

Make sure the distributor is correctly positioned. On Vortex engines, the cap wiring layout can be tricky — the spark plug wire connection point does not always align with where the rotor physically points when sparking occurs.

I'm confident that the rotor is pointing to piston #2 on the cap. The engine simply will not start. I’ve tried using starter fluid in the throttle body, but no spark or ignition response. It’s been sitting for about nine months — could stale fuel be the issue? That said, I suspect it's more mechanical than fuel-related.

DTC P1345: Crankshaft Position (CKP) - Camshaft Position (CMP) Correlation. This is a GM-specific code — the engine will not allow starting until it confirms proper alignment between crank and camshafts. You've replaced the crankshaft sensor, but have you checked or replaced the camshaft position sensor? The most likely cause is improper mechanical alignment of the two shafts. You should verify alignment using vehicle service manuals or resources like http://www.alldata.com. Also check that both sensors are moving freely — ensure no physical obstruction. Check fuses and relays related to crank/cam sensors. Why else would this code appear?

Try loosening the distributor slightly and rotating it manually in either direction to see if you can get a spark. If not, towing the vehicle to a professional mechanic or dealer for proper diagnostics may be necessary. Using an oscilloscope to observe camshaft and crankshaft sensor signals is the most accurate way to confirm signal integrity.

Most likely explanation: The distributor was installed one tooth off. Since the camshaft position sensor is located in the distributor, a single-tooth misalignment can cause P1345. This is very common on Vortex engines. Loosening the distributor won’t fix this issue — some Vortex models actually prevent rotation beyond a certain point due to design constraints. Quick test: Lift the distributor slightly and rotate it one tooth in each direction. If no spark occurs, try the opposite direction. Also verify that the distributor shaft is turning (the rotor should spin when manually rotated).

Good point — I’ve seen multiple cases where older small-block engines were incorrectly installed with the oil pump drive gear misaligned, and people still tightened everything down without checking. Some mechanics have had to drill a small hole in the distributor base to allow for additional adjustment — though this is more often due to chain stretch than alignment issues.

Thanks! I’ll try that later today. The distributor shaft appears to be turning because when I rotate it, the rotor spins. However, after attempting to start the engine and failing, I notice that my #1 piston is at TDC on compression stroke — but the rotor no longer matches its original position. Why does this happen? Is there a mechanical issue or sensor drift?

This strongly suggests the distributor is not properly aligned with the oil pump drive gear.

Possibility: The distributor's internal drive gear is worn. However, I believe this would have been noticeable during installation or initial inspection.

We could always hope! :)

Hi teamster147 — I’ve had the same issue and still experience it slightly. If you don’t mind, where or who did you buy your rebuilt engine from? Any recommendations?