Engine

P0379 — Timing Reference High Resolution Signal B – No Pulses

Severity: high Drive with care, to a shop

What P0379 means

The engine control module relies on crankshaft and camshaft position signals to time fuel injection and spark precisely. P0379 sets when no pulses arrive on high-resolution timing reference channel B while the engine should be turning. Without that signal the ECM loses its precise reference to engine position.

Symptoms

  • Check Engine light on
  • Hard starting or no start
  • Rough idle or misfires
  • Loss of power and hesitation
  • Engine stalling while driving
  • Engine cranks but will not fire

Possible causes

  1. Failed crankshaft or camshaft position sensor
  2. Open, shorted or chafed wiring
  3. Corroded or loose sensor connector
  4. Damaged, dirty or misaligned reluctor (trigger) wheel
  5. Incorrect sensor air gap or poor mounting
  6. Internal ECM fault or input circuit failure (uncommon)

How to diagnose

  1. Scan for all codes and freeze-frame data, and look for related crank or cam sensor codes
  2. Watch RPM on the scan tool while cranking to see if the ECM registers engine speed
  3. Inspect sensors, connectors and harness for oil, chafing, corrosion and loose fit
  4. Test sensor power, ground and signal wire with a multimeter per the wiring diagram
  5. Scope the sensor signal while cranking to check for a clean pulse pattern
  6. Remove the sensor and inspect the reluctor wheel for damaged teeth, debris or play
  7. Check sensor air gap and seating, and verify timing marks if a belt or chain was recently serviced
  8. If wiring and sensor are good, test ECM power and grounds before suspecting the module

Common fixes

  • Replace the faulty crankshaft or camshaft position sensor
  • Repair damaged wiring, replace the connector or clean the terminals
  • Replace or correct the reluctor wheel and set the proper sensor gap
  • Correct engine timing if it is off
  • Repair or replace the ECM once it is confirmed faulty

Questions and answers

What does P0379 mean?

The ECM is not receiving pulses on high-resolution timing reference signal B from a position sensor. The usual culprits are the sensor, its wiring or the reluctor wheel.

Can I drive with P0379?

It is risky. The engine can stall at any time and may not restart. Drive only as far as needed to reach a repair shop.

How do I fix P0379?

Start by inspecting the sensor connector and wiring, then test the crank and cam sensors. Most cases end with a new sensor or a wiring repair, and the ECM is rarely the cause.

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.