P0337

What it means

P0337 means the engine control unit has detected a low voltage signal in the crankshaft position sensor 'A' circuit. The ECU expects a switching signal from the sensor as the engine turns, and it saw the circuit sitting below the expected voltage range, which points to a short to ground, an open circuit or a failing sensor. The crankshaft signal is vital for engine speed, ignition timing and fuel injection timing.

Symptoms

• Engine cranks but will not start
• Engine stalls suddenly while running or when coming to a stop
• Intermittent misfire or hesitation
• Rev counter drops to zero or behaves erratically
• Check engine light on
• Hard or long cranking before the engine fires

Possible causes

• Faulty crankshaft position sensor (internal failure, often heat related)likely
• Damaged, chafed or shorted sensor wiring (signal wire shorted to ground or open circuit)likely
• Corroded, loose or contaminated sensor connector or terminalslikely
• Sensor supply or ground fault from the ECU or a related circuitpossible
• Metallic debris on the sensor tip or a damaged reluctor or trigger wheel causing a weak or missing signalpossible
• Incorrect sensor air gap or loose sensor mountingpossible
• Faulty engine control unitrare

How to diagnose

1. Read the stored codes and freeze frame data to see engine speed, temperature and conditions when the fault set, and check for related camshaft sensor codes
2. Inspect the sensor, its wiring and the connector for heat damage, oil contamination, chafing, corrosion and bent or pushed-back pins
3. Check the live engine speed reading while cranking; no reading suggests a signal loss at the sensor or in the wiring
4. Check the sensor mounting, and look at the sensor tip for metal debris or damage
5. Test the sensor supply voltage and ground at the connector against the manufacturer's specification, as the sensor type (Hall effect or inductive) varies by model
6. Test the signal wire for continuity and for short to ground between the sensor and ECU with the battery disconnected
7. Inspect the reluctor or trigger wheel for damage or missing teeth where access allows, and view the signal on an oscilloscope if available
8. Wiggle-test the harness with the engine cranking or running to find intermittent faults

How to fix

• Replace the crankshaft position sensor with a quality part suited to the vehicle
• Repair or replace damaged wiring, and secure the harness away from heat and moving parts
• Clean or replace corroded connectors and terminals
• Correct any supply or ground fault found in the circuit
• Clear debris, refit the sensor correctly and set the specified air gap, or repair a damaged trigger wheel
• Have the ECU checked or replaced only after all wiring and sensor faults are ruled out

Can I keep driving?

Nearby codes

• P0336GenericCrankshaft Position Sensor A Circuit Range/Performance
• P0338GenericCrankshaft Position Sensor A Circuit High