1999 Suburban P1345 Code: Cam Sensor Replacement Failed, Still Getting Lean on Bank 2 - Help Needed

Timing chain slack could be a contributing factor; also consider a crankshaft sensor issue, though the engine starts fine.

The crankshaft sensor is functioning — the engine starts and runs. However, I suspect timing chain issues or misalignment. The exhaust fumes are rich, which contradicts the lean O2 readings on bank 2.

Rich exhaust fumes suggest the Powertrain Control Module (PCM) is injecting maximum fuel to compensate for a perceived lean condition; however, the oxygen sensor may still report a lean state due to improper feedback loop.

It's possible that bank 1 is running rich, which causes the O2 sensor on bank 2 to only monitor fuel delivery from its own injectors. This could lead to misreadings and false lean codes on bank 2.

The P1345 code may be directly related to the oxygen sensor readings — it's worth verifying if other engine sensors or fuel delivery systems are contributing to this issue before continuing with camshaft repairs.

I believe the lean condition on bank 2 is tied to incorrect ignition timing. Even a slight misalignment could cause improper combustion and trigger both lean codes and cam sensor issues. This side of the engine should be addressed before focusing solely on the camshaft position.

When I first got this truck, it was running poorly. After enabling closed-loop operation, my code reader showed P1345 and lean codes. I replaced the cam sensor — no improvement. The code returned at startup. I checked timing with diagnostic tools and found both distributor and timing chain misaligned (off by one tooth). Correcting this improved engine performance temporarily, but the P1345 code disappeared. However, after further testing, I noticed that when the distributor was set to 180 degrees out from number 1, the engine wouldn't start. I also replaced the CPI sensor and now see additional codes: P0174 (bank 2 rich), P0151 (O2 sensor failure on bank 2), and P1153 (fuel system issue). I still believe timing or ignition alignment is at fault, but I'm not certain if it's a mechanical or electrical problem.

Yes — the distributor appears to be set 180 degrees out of phase with number 1 cylinder.

Correct, but after adjusting the distributor, the engine won't start. I've also replaced the CPI sensor and now see P0174 (bank 2 rich), P0151 (O2 sensor failure on bank 2), and P1153 (fuel system issue).

Start by ensuring the distributor is properly aligned. Then verify fuel pressure — if it's dropping or inconsistent, that could explain both lean and rich conditions.

Check the evaporative emissions system — ensure all hoses are intact and not clogged or damaged. If the system is compromised, it may affect fuel delivery and trigger O2 sensor errors. After checking the EVAP lines, inspect the evap purge valve solenoid for proper operation.

Should I leave the distributor in its current position or realign it properly?

It sounds like a professional diagnosis of ignition timing and base engine timing is needed — as suggested by Comp. A misaligned distributor or faulty timing chain could be causing both P1345 and the lean/rich discrepancies.