What causes fault code P0371?

• Most likely: Electromagnetic interference (EMI) on the signal wire from ignition components or alternator • Likely: Faulty high-resolution sensor (optical or magnetic sensor internal failure) • Possible: Damaged or dirty reluctor wheel/encoder disk causing false pulses • Rare: Poor connection or corrosion in the sensor wiring harness connector

How do you fix fault code P0371?

STEP 1: Inspect wiring and connectors for chafing or corrosion. Ensure signal wires are routed away from high-voltage ignition components to prevent EMI. STEP 2: Perform voltage testing. The sensor typically requires a stable 5V or 12V reference and a clean ground (<0.1V). STEP 3: Use an oscilloscope to monitor the waveform of Signal A. Look for noise or additional spikes in the signal. It should be a crisp square wave. STEP 4: If extra pulses are seen on the scope but the reluctor wheel is clean and intact, replace the high-resolution sensor. STEP 5: Clear the DTC and perform a test drive to verify the fix.

Powertrain (Engine & Gearbox)Standard EOBD

P0371 - Timing Reference High Resolution Signal A Too Many Pulses

Q: What does fault code P0371 mean?

P0371 is set when the Engine Control Module (ECM/PCM) detects more pulses than expected from the high-resolution timing reference signal A. This signal is typically generated by an optical sensor or a high-frequency crankshaft/camshaft sensor. The ECM uses this signal for precise fuel injection and ignition timing. If the pulse count exceeds the calibrated threshold per engine revolution, the ECM loses synchronization integrity, which often triggers a limp-home mode to prevent engine damage caused by incorrect timing.

Q: What are the symptoms of fault code P0371?

• Check Engine Light (MIL) illumination • Engine hesitation or stumbling during acceleration • Sporadic engine stalling • Hard starting condition • Reduced engine power (Limp mode) • Failed emission inspection due to active DTC

Last updated:1 February 2026

Related:Crankshaft Position Sensor, Camshaft Position Sensor, Optical Sensor, PCM/ECU, Distributor

System

Powertrain (Engine & Gearbox)

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P0300

Random or Multiple Cylinder Misfire Detected

P0301

Cylinder 1 Misfire Detected

P0302

Cylinder 2 Misfire Detected

P0303

Cylinder 3 Misfire Detected

Technical Description

P0371 is set when the Engine Control Module (ECM/PCM) detects more pulses than expected from the high-resolution timing reference signal A. This signal is typically generated by an optical sensor or a high-frequency crankshaft/camshaft sensor. The ECM uses this signal for precise fuel injection and ignition timing. If the pulse count exceeds the calibrated threshold per engine revolution, the ECM loses synchronization integrity, which often triggers a limp-home mode to prevent engine damage caused by incorrect timing.

Possible Causes

Electromagnetic interference (EMI) on the signal wire from ignition components or alternator

Faulty high-resolution sensor (optical or magnetic sensor internal failure)

Damaged or dirty reluctor wheel/encoder disk causing false pulses

Poor connection or corrosion in the sensor wiring harness connector

Symptoms

Check Engine Light (MIL) illumination

Engine hesitation or stumbling during acceleration

Sporadic engine stalling

Hard starting condition

Reduced engine power (Limp mode)

Failed emission inspection due to active DTC

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P0371 - Timing Reference High Resolution Signal A Too Many Pulses

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P0371 - Timing Reference High Resolution Signal A Too Many Pulses

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