What causes fault code P0379?

• Most likely: Faulty optical sensor or crankshaft/camshaft sensor (Signal B) • Likely: Wiring issues (open circuit or short in the signal wire) • Possible: Damaged or fouled trigger wheel (dirt, oil, or physical damage) • Rare: Internal Engine Control Unit (ECU) fault

Powertrain (Engine & Gearbox)Standard EOBD

P0379 - Timing Reference High Resolution Signal B No Pulses

Q: What are the symptoms of fault code P0379?

• Engine will not start (No start condition) • Engine stalls suddenly while driving • Check Engine Light (MIL) illuminated • Engine hesitation or misfiring prior to total signal loss

Q: How do you fix fault code P0379?

STEP 1: Inspect the sensor connector for corrosion or loose pins. Clean as necessary. STEP 2: Use a multimeter to verify power supply to the sensor (typically 5V or 12V) and check the ground circuit. Signal wire resistance should be < 1 Ohm. STEP 3: Perform an advanced diagnosis using an oscilloscope. Monitor the waveform of Signal B while cranking the engine. A consistent square wave should be present. If no signal is present despite correct power/ground, the sensor is faulty. STEP 4: Inspect the trigger wheel for mechanical damage or debris (e.g., metal shavings). Clean or replace if necessary. STEP 5: If the sensor is confirmed faulty, replace the component and clear fault codes.

Last updated:1 February 2026

Related:Crankshaft Position Sensor, Camshaft Position Sensor, Optical Sensor, Engine Control Module (ECM/ECU), Wiring Harness

System

Powertrain (Engine & Gearbox)

Related Fault Codes

P0300

Random or Multiple Cylinder Misfire Detected

P0301

Cylinder 1 Misfire Detected

P0302

Cylinder 2 Misfire Detected

P0303

Cylinder 3 Misfire Detected

Technical Description

P0379 is a generic OBD-II code indicating that the Engine Control Unit (ECU) has detected a lack of pulses from the high-resolution timing reference signal 'B'. This signal is typically generated by an optical or Hall-effect sensor within the distributor or on the crankshaft/camshaft assembly. The sensor monitors a trigger wheel with many fine increments to provide the ECU with precise engine position data. If the signal is missing entirely for a calibrated period or number of engine revolutions, the code is set. This failure disrupts fuel injection timing and ignition synchronization, often resulting in a no-start condition or engine stalling.

Possible Causes

Faulty optical sensor or crankshaft/camshaft sensor (Signal B)

Wiring issues (open circuit or short in the signal wire)

Damaged or fouled trigger wheel (dirt, oil, or physical damage)

Internal Engine Control Unit (ECU) fault

Symptoms

Engine will not start (No start condition)

Engine stalls suddenly while driving

Check Engine Light (MIL) illuminated

Engine hesitation or misfiring prior to total signal loss

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P0379 - Timing Reference High Resolution Signal B No Pulses

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P0379 - Timing Reference High Resolution Signal B No Pulses

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