P0337: OBD-II code P0337 flags a low or missing signal from the crankshaft position sensor — the PCM isn't getting a valid crank reference for ignition and injection timing.

Symptoms

• Check engine light is on; the engine may crank but refuse to start because there is no spark or fuel command.
• If the engine does start, it may run erratically or stall as the PCM struggles for a timing reference.
• Companion misfire and cam correlation codes usually appear alongside P0337.

Common causes

• A failed crank sensor with an open or shorted internal element.
• A shorted-to-ground signal wire between the sensor and the PCM.
• An excessive air gap between the sensor tip and reluctor wheel from a loose mount or damaged bracket.

What to do?

Measure the sensor's signal wire voltage during cranking with an oscilloscope or capable scan tool. Check sensor resistance (varies by type). Verify the sensor mounting bolt is torqued to spec and the sensor tip is clean of metal debris. Replace the sensor if the signal is missing or intermittent.