If your car’s check engine light came on and a scan tool returned code P1339, you’re likely seeing it because the engine control module detected an issue with the crankshaft position sensor signal specifically, a mismatch between what the crankshaft and camshaft sensors are reporting. This isn’t just a random glitch; it means the powertrain control module (PCM) can’t reliably determine engine timing, which affects fuel delivery and spark timing. Ignoring it may lead to rough idling, stalling, or failure to start.

What does code P1339 actually mean?

P1339 is a manufacturer-specific OBD-II diagnostic trouble code used by General Motors (GM), including Chevrolet, GMC, Buick, and Cadillac models. It stands for “Crankshaft Position (CKP) Sensor and Camshaft Position (CMP) Sensor Correlation – Bank 1.” In plain terms: the PCM expects the crank and cam signals to line up in a predictable pattern during engine rotation and when they don’t, it sets P1339. It’s not about one sensor failing outright, but about their relationship being out of sync.

When do drivers usually see this code?

You’ll most often encounter P1339 after recent engine work like replacing the timing chain, water pump, or distributor or if the crank or cam sensor was disturbed, misaligned, or installed incorrectly. It also appears after sensor wiring damage, corrosion at connectors, or a worn timing chain that’s stretched enough to throw off phasing. Some drivers report it popping up intermittently during cold starts or after the vehicle sits overnight, especially in older GM 3.1L, 3.4L, or 3.8L V6 engines.

What’s the difference between P1339 and similar codes like P0340 or P0335?

Unlike P0340 (camshaft position sensor circuit malfunction) or P0335 (crankshaft position sensor circuit malfunction), P1339 doesn’t point to a dead sensor or open circuit. Instead, it flags a timing correlation fault so both sensors may be electrically functional, but their signals aren’t aligning as expected. That’s why simply swapping sensors without checking mechanical timing often doesn’t fix it. You can read more about how this differs from other related codes in our diagnostic trouble code P1339 description.

Common mistakes people make diagnosing P1339

Practical steps to verify and fix P1339

Start with a visual check: look for oil contamination on the crank or cam sensor tips, frayed or pinched wiring near the timing cover, or loose sensor mounting. Then confirm mechanical timing on many GM V6s, that means lining up the crank pulley mark with the timing tab and ensuring the cam sprocket dot lines up with the cylinder head surface. If timing is off by even one tooth, P1339 will set. You’ll also want to inspect the crank reluctor wheel for missing or bent teeth a common cause on high-mileage engines. For a full list of verified causes and fixes, see our guide on P1339 code causes and solutions.

Is P1339 safe to ignore?

No. While some vehicles may run temporarily with P1339 stored, the PCM may enter limp mode, reduce power, or cut fuel to protect the engine. In worst cases, severe misfires or no-start conditions develop. It’s also a sign of underlying wear like a stretched timing chain that could worsen quickly. If you’re unsure whether timing is correct, it’s safer to have it checked than risk internal engine damage.

Before you clear the code or replace parts, double-check timing marks, inspect both sensors and their mounting surfaces, and scan for pending or history codes. If the code returns immediately after clearing and relearning, suspect mechanical timing or a damaged reluctor ring not just the sensors. You can find the exact meaning behind the code number and how it fits into GM’s diagnostic logic in our P1339 vehicle diagnostic code meaning page.

For reference, the Society of Automotive Engineers (SAE) defines correlation-based timing codes like P1339 in SAE J2012, which outlines standardized diagnostic trouble code definitions across manufacturers.

Next step: With the key off, inspect the crankshaft position sensor mounting area for oil leaks or metal shavings. Then, using a socket and breaker bar, slowly rotate the crankshaft clockwise while watching the camshaft sprocket both should move smoothly and in sync. If the cam jumps or hesitates, the timing chain may be stretched or the tensioner failed.