Engine

P0373 — Crankshaft Timing Reference Signal A Intermittent or Erratic

Severity: medium Drive with care, to a shop

What P0373 means

The engine control module continuously compares pulses from the crankshaft position sensor (and sometimes the camshaft sensor) with the pattern expected from the reluctor wheel. P0373 sets when high-resolution timing signal A drops out or shows extra, erratic pulses. The ECM uses this signal to calculate engine speed and set ignition and injection timing, so a bad signal upsets how the engine runs.

Symptoms

  • Check Engine light on
  • Hard starting or no start
  • Rough idle or hesitation under acceleration
  • Loss of power
  • Stalling, often when the engine is hot
  • Erratic tachometer readings

Possible causes

  1. Failing or contaminated crankshaft position sensor
  2. Damaged wiring, open or shorted circuit in the sensor harness
  3. Corroded or loose sensor connector
  4. Damaged, dirty or shifted reluctor wheel (tone ring)
  5. Loose sensor mounting or incorrect air gap
  6. Electrical interference, such as from bad spark plug wires or a poor ground
  7. Faulty ECM (rare)

How to diagnose

  1. Scan for codes and freeze frame data, and look for related crank or cam codes such as P0335 or P0340.
  2. Inspect the sensor, connector and harness for chafing, oil, moisture and corrosion.
  3. Check that the sensor is secure and the air gap is correct.
  4. Remove the sensor and inspect its tip and the reluctor wheel for metal debris, dirt, or damaged or bent teeth.
  5. Test the power, signal and ground wires with a multimeter, and wiggle the harness with the engine running while watching RPM.
  6. Check sensor resistance (inductive type) or supply voltage, and view the waveform with a scope against specs.
  7. Check engine grounds and battery condition to rule out interference.
  8. If everything checks out, test the ECM and its power supply.

Common fixes

  • Replace the crankshaft position sensor
  • Repair the wiring or replace a damaged connector
  • Clean, straighten or replace the reluctor wheel
  • Correct sensor mounting and air gap
  • Reflash or replace the ECM only if confirmed faulty

Questions and answers

What does P0373 mean?

The ECM is getting an intermittent or erratic high-resolution timing signal from the crankshaft position sensor circuit. The sensor, wiring or connector is the most common culprit.

Can I drive with P0373?

Only as far as needed to get it repaired. The engine may stall at any moment, which is dangerous while driving.

Will clearing the code fix it?

No. If the cause remains, the code returns and the engine can stall again. Inspect the sensor, wiring and reluctor wheel first.

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.