P1345 is a GM diagnostic trouble code that is often observed on the older 5.7L and 4.3L Vortec engines (pre-LS). These engines will be the focus of this article. Most newer engines will trigger a different code for crank/cam correlation.
The crank and cam sensors always record the crank and cam position. When the positions no longer agree with one another, DTC P1345 is triggered and causes the check engine light to come on.
P1345 Definition: Crankshaft Position to Camshaft Position Correlation
P1345 is pretty self-explanatory. It occurs then the camshaft and crankshaft positions, as recorded by their respective sensors, no longer correlate with one another.
Symptoms
Here are the most common symptoms associated with P1345:
- Rough idle
- Stallling/Pinging
- Misfiring
- Other trouble codes (P0335 and P0340 in particular)
- Rough/No start
P1345 Diagnosis
Here are the common causes of P1345, as well as a solid order of diagnostic operations:
1. Check for Other Codes
P0340 or P0335 often accompanies P1345.
- P0340– Bad Camshaft Position Sensor– The camshaft position sensor is on the distributor of the 4.3 and 5.7. If you have P0340, it’s almost always either a bad cam sensor or the wiring to it has gone bad. Here’s a good video that’ll walk you through replacing it (YouTube).
- P0335– Bad Crankshaft Position Sensor– The crankshaft position sensor is right behind the harmonic balancer on the 5.7, which is actually much easier to get to than an LS motor. Here’s a super quick video showing you how to get to it.
Fixing either of these codes will take P1345 with it 99% of the time.
2. Wiring Issues
Take a look at the wiring harness going to the crank and camshaft sensors. Make sure that they are not burnt, damaged, or frayed.
Most of these GM vehicles that get these codes are pushing 25 years old. That’s a lot of time exposed to the elements.
3. Distributor
If the distributor goes bad or is improperly aligned, it will cause 1345. The distributor is a great place to start IF P1345 is the only code that came up when you plugged your scanner into the OBD2 port.
Distributors have a rotating arm that sends a spark to the plugs at the correct time. If it is improperly aligned, the camshaft position sensor won’t line up right, and P1345 will occur (the engine should be misfiring or pinging while this happens)
4. Bad Timing Chain
The Vortec 5.7 and 4.3 engines use very sturdy timing chains that rarely break or jump a tooth. But, it can happen.
If the timing chain jumps a tooth, that would mean both sensors are telling the truth, and the correlation between crank and cam is off. This scenario is way less likely than a distributor problem.
Vehicles Where P1345 is Commonly Observed
- GMT400 Chevy Silverado
- GMT400 GMC Sierra
- GMC Jimmy
- Chevy Blazer
- Chevy Express
Conclusion
Make sure to cross-reference the codes mentioned above. If there are none, start with the distributor, as that’ll be the most likely cause of P1345 if there are no codes. Good luck repairing your vehicle!