Ignition

P0338 — Crankshaft Position Sensor A Circuit High Input

Severity: medium Drive with care, to a shop

What P0338 means

The engine control module reads the crankshaft position sensor constantly to know engine speed and piston position, and uses it to time spark and fuel injection. P0338 sets when the voltage in the sensor A circuit is higher than expected. The cause can be the sensor, a wire shorted to voltage, a poor ground or, rarely, the module itself.

Symptoms

  • Check engine light on
  • Hard starting or no start
  • Misfires and rough idle
  • Loss of power or hesitation when accelerating
  • Engine stalling
  • Poor fuel economy

Possible causes

  1. Failed crankshaft position sensor
  2. Damaged wiring or connector, or a short to voltage in the circuit
  3. Poor sensor ground connection
  4. Charging system over-voltage affecting the reference supply
  5. Faulty ECM (rare)

How to diagnose

  1. Scan for codes and freeze frame data, and look for related crankshaft or camshaft sensor codes
  2. Inspect the sensor, connector and harness for oil, chafed insulation, corrosion or a loose fit
  3. Check the sensor's reference voltage and ground at the connector using the vehicle wiring diagram
  4. Test the harness for a short to power or an open circuit between the sensor and the ECM
  5. Measure inductive sensor resistance or view the signal on a scope while cranking
  6. Check battery voltage and alternator output
  7. Inspect the reluctor wheel and sensor air gap where applicable
  8. If wiring and sensor are good, test the ECM

Common fixes

  • Replace the crankshaft position sensor
  • Repair or replace damaged wiring and connectors
  • Clean and tighten ground connections
  • Repair the charging system fault if present
  • Replace or reprogram the ECM (rare)

Questions and answers

What does P0338 mean?

The ECM detects a voltage that is too high in the crankshaft position sensor A circuit. The sensor or its wiring is the usual cause, less often a ground issue or the ECM.

Can I drive with a P0338 code?

Only a short distance, such as to a shop. The engine can stall at any moment and may not restart, so don't put off diagnosis.

Will replacing the sensor fix it?

Not always. Check the wiring, connector and ground first: if a wire is shorted to voltage, a new sensor may fail or the code may come back.

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.