Engine

P0371 — Timing Reference High Resolution Signal A: Too Many Pulses

Severity: medium Drive with care, to a shop

What P0371 means

The engine control module counts pulses from the crankshaft (sometimes camshaft) position sensor and compares them with what it expects for the engine's speed and position. It uses these pulses, generated by the teeth on a reluctor wheel, to time ignition and fuel injection. P0371 sets when more pulses arrive than expected, which points to electrical noise, a sensor problem or a damaged tone ring.

Symptoms

  • Check engine light on
  • Rough idle
  • Hesitation or stumbling under acceleration
  • Hard starting or long cranking
  • Reduced power
  • Stalling
  • Misfire
  • No-start in some cases

Possible causes

  1. Failed crankshaft or camshaft position sensor
  2. Damaged, corroded or loose wiring or connector in the sensor circuit
  3. Electrical interference on the signal wire from poor shielding or nearby high-current wiring
  4. Damaged or misaligned reluctor (tone) wheel
  5. Metal debris or dirt on a magnetic sensor tip
  6. Wrong sensor installed
  7. Rarely, a faulty ECM/PCM

How to diagnose

  1. Scan for codes and freeze frame data, and note any other CKP or CMP codes
  2. Inspect the sensor connector and harness for chafing, corrosion, oil and poor terminal contact
  3. Remove the sensor and check its tip for metal shavings or damage
  4. Verify sensor mounting and air gap
  5. Inspect the reluctor wheel for broken or bent teeth, cracks, debris and runout
  6. Test sensor resistance, power, ground and signal against the factory wiring diagram
  7. Use an oscilloscope to view the signal at idle and while cranking, looking for extra pulses or noise
  8. Confirm the part number matches the engine

Common fixes

  • Replace the crankshaft or camshaft position sensor
  • Repair or replace damaged wiring and connectors
  • Clean debris from the sensor and its mounting area
  • Replace or properly reinstall the reluctor wheel
  • Reprogram or replace the ECM only after everything else is ruled out

Questions and answers

What does P0371 mean?

The engine computer is receiving more timing pulses than expected from the crankshaft or camshaft sensor. The usual causes are the sensor, its wiring or the tone ring.

Can I drive with P0371?

Only a short trip to get it checked. The engine may misfire, lose power or stall, which can be dangerous in traffic.

Will replacing the sensor fix it?

Not always. If the cause is wiring, interference or a damaged reluctor wheel, a new sensor won't help, so test the whole circuit 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.