Ignition

P0337 — Crankshaft Position Sensor A Circuit Low Input

Severity: high Do not drive

What P0337 means

The engine computer reads the crankshaft position sensor to know crank angle and engine speed, which it uses to time spark and fuel injection. P0337 sets when that signal is lower than expected or missing. A weak or lost signal leads to rough running, stalling or a no-start.

Symptoms

  • Check Engine light on
  • Hard starting or no start
  • Rough or erratic idle
  • Hesitation and reduced power
  • Engine stalling at idle or under load

Possible causes

  1. Failed crankshaft position sensor
  2. Damaged or corroded wiring or connector in the sensor circuit
  3. Signal wire shorted to ground
  4. Damaged reluctor ring or excessive sensor air gap
  5. Poor sensor ground or low reference voltage
  6. PCM input circuit failure (uncommon)

How to diagnose

  1. Scan for codes and freeze frame data, and look for related codes such as a camshaft sensor fault.
  2. Inspect the sensor, connector and harness for oil, chafing, corrosion or a loose fit.
  3. Check whether the scan tool shows RPM while cranking and whether the tachometer moves.
  4. Measure sensor resistance (for inductive types) and compare to spec.
  5. Check sensor power, ground and signal with a multimeter or scope.
  6. Test the wiring to the PCM for opens and shorts to ground.
  7. Inspect the reluctor ring for damage or debris and verify air gap and mounting.
  8. If wiring and sensor are good, evaluate the PCM.

Common fixes

  • Replace the crankshaft position sensor
  • Repair the wiring or replace the connector
  • Clean or replace the reluctor ring and correct the air gap
  • Restore sensor ground and power supply
  • Repair or replace the PCM (last resort)

Questions and answers

Can I drive with a P0337 code?

It is best not to. The engine may stall suddenly and then refuse to restart, which is dangerous on the road. Drive only as far as needed to get it repaired.

What does P0337 mean in simple terms?

The computer is getting a weak or missing signal from the crankshaft sensor. Without it, it can't tell where the engine is in its rotation to time spark and fuel.

Will replacing the sensor fix P0337?

Not always. Wiring, connectors or grounds are often to blame. Test the circuit and air gap first, then replace the sensor if it fails.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.