P0379
Timing Reference High Resolution Signal B No Pulses
If your code reader dashboard displays the generic DTC error code P0379, your vehicle is currently experiencing an active failure related to "Timing Reference High Resolution Signal B No Pulses". Proper system troubleshooting is required to safely clear this warning.
Driver's Summary
Your vehicle's computer logged P0379 after detecting a malfunction in the timing reference high resolution signal b no pulses system. You may notice engine cranks but won't start, all of which are direct consequences of this malfunction. This is a serious fault — avoid extended driving and have your vehicle inspected by a mechanic as soon as possible to prevent further damage.
Symptoms
Engine cranks but won't start
Common Causes
- Dead sensor B
- Unplugged harness
- Broken wire in the circuit
- PCM fault
How to Fix
- 1 Replace sensor B
- 2 Reconnect wiring harness
- 3 Repair broken circuit
- 4 Diagnose PCM
Technical Explanation
To set P0379, the PCM samples the affected circuit multiple times per second, comparing live readings against manufacturer-programmed operating windows. Misfire rate is counted per cylinder over rolling windows and compared against two thresholds: a catalyst-damaging rate (triggers flashing MIL) and an emissions-exceeding rate (triggers solid MIL). The PCM logs which cylinder is misfiring based on crankshaft position at the time of each detected event. Once confirmed, the code is stored as a permanent DTC and the MIL is activated. The freeze frame snapshot — recording RPM, load, coolant temperature, and fuel trim at fault detection — is also saved and is critical for accurate diagnosis.
Is It Safe to Drive?
With P0379 active, your engine or transmission is not operating within design parameters. Short-term driving may seem fine, but internal damage is accumulating — particularly to dead sensor b.
Mechanic's Pro Tip
Before replacing any component on P0379, spend 5 minutes inspecting the wiring harness and connector first — corrosion, chafed insulation, and backed-out pins cause the majority of these faults and cost nothing to fix. Use a multimeter to measure voltage drop across the connector pins under load; anything above 0.1V indicates excessive resistance that will cause intermittent failures even after replacing the sensor.
Sensor replacement: 150 - 400