P0337
Crankshaft Position Sensor A Circuit Low Input
If your vehicle's onboard computer has flagged the diagnostic trouble code P0337, it refers to a detected anomaly regarding "Crankshaft Position Sensor A Circuit Low Input". This systemic engine fault needs a targeted check before symptoms expand.
Driver's Summary
P0337 is triggered when the PCM detects an abnormal condition associated with crankshaft position sensor a circuit low input. Typical symptoms include engine cranks but will not start, stalling, no tachometer signal. Given the high severity of this code, continuing to drive risks significant mechanical damage. Have it diagnosed immediately.
Symptoms
Engine cranks but will not start, stalling, no tachometer signal
Common Causes
- Short to ground in crank sensor wiring
- Failed crankshaft position sensor
- Dead battery
- Bad PCM
How to Fix
- 1 Trace and repair shorted wire
- 2 Replace crankshaft position sensor
- 3 Test and charge battery
- 4 Test PCM
Technical Explanation
Code P0337 is confirmed when the ECM's diagnostic algorithm detects a parameter deviation that persists across a defined number of consecutive drive cycles. For injector-specific codes, the ECM monitors the injector control circuit voltage drop during each pulse; a shorted or open injector presents a characteristic resistance signature that differs measurably from a healthy unit. The MIL illuminates after the fault is confirmed on two consecutive drive cycles, and the freeze frame data captured at first detection is stored in the PCM's memory for diagnostic reference.
Is It Safe to Drive?
An active P0337 code under high-severity conditions means the affected system is operating outside safe parameters. Continued driving — especially under load or at highway speeds — significantly increases the risk of secondary damage to components like failed crankshaft position sensor.
Mechanic's Pro Tip
Module replacement should always be the last resort for P0337 after exhaustively verifying all power supply circuits, ground connections, and communication bus wiring. Use a wiring diagram to locate all fuses, relays, and ground points for the affected module, and measure voltage drop on each ground with the circuit loaded. A module "failure" is frequently a corroded ground eyelet or a weak battery causing brownout conditions — fix these first and you'll save hundreds of dollars on an unnecessary module replacement.
Crank sensor replacement: 150 - 350