P0379 — Timing Reference High Resolution Signal B No Pulses

Does P0379 always mean the timing-reference sensor is defective?

No. P0379 can also result from damaged wiring, a bad connector, sensor misalignment, a missing encoder target, or loss of sensor power or ground.

Can the vehicle be driven with P0379 stored?

Driving is not recommended because the engine may lose synchronization and stall suddenly, potentially creating a traffic hazard.

What should be checked first when P0379 is present?

Start with the Signal B sensor connector, wiring, mounting, air gap, and reluctor or encoder target before replacing any components.

Why might P0379 appear intermittently?

Heat, vibration, moisture, or terminal movement can temporarily interrupt the Signal B circuit, while a failing sensor pickup may also lose its output intermittently.

The engine control unit logs code P0379 when it stops receiving the high-resolution timing reference signal on circuit B. This signal tells the computer exactly where the crankshaft and camshafts are positioned, which the ECU needs to fire the injectors and spark plugs at precisely the right moment. Without a clean, consistent signal, the engine loses its timing map and can't run efficiently.

The ECU watches this signal every time you drive. It expects a steady stream of pulses from the reference sensor or tone wheel. When those pulses disappear or become erratic for enough consecutive drive cycles, the computer confirms a genuine fault and sets P0379. The check engine light comes on, and a freeze frame snapshot records the engine's operating conditions at the moment the problem appeared—RPM, load, temperature, and vehicle speed all get stored. That snapshot is the best clue about what was happening when the signal dropped out.

P0379 indicates a hardware or wiring problem in the high-resolution timing circuit, not a sensor that read out of range. The ECU isn't saying a sensor is broken—it's saying the signal stopped arriving entirely. Finding why requires checking the entire path from sensor to computer.

Common Symptoms of P0379

The check engine light will be illuminated, which is the most obvious sign that P0379 is present. Depending on which system depends on that timing signal, the car may enter limp mode and restrict power or disable certain functions. Fuel economy often drops because the engine runs on a default timing map instead of the precise calibration it normally uses. In some cases the affected system—variable valve timing, fuel injection, or ignition—operates intermittently or cuts out completely. Some vehicles feel sluggish or stumble under load, while others run rough at idle. The exact symptoms depend on whether one or both camshaft reference channels are affected.

What Causes P0379?

The signal can be lost at several points in the circuit. A blown fuse that feeds power to the reference sensor or its circuit will cut the signal immediately. A poor ground connection at the sensor or the ECU can corrupt the signal or prevent it from being processed correctly. Wiring that is broken, chafed through, or pinched against metal creates an open circuit or intermittent short that blocks the signal. Corroded, loose, or physically damaged connectors introduce resistance or complete disconnects. On the control side, the ECU's own driver circuit for that channel can fail, though this is less common than wiring problems.

How to Diagnose P0379

Begin by connecting an OBD2 scanner and confirming that P0379 is stored, then record all freeze frame data. This information tells you exactly what the engine was doing when the signal disappeared, which helps narrow down whether the problem is temperature-related, load-related, or happens all the time.

Check for any other stored trouble codes before clearing anything. Related codes in the same circuit often point to the real root cause. Look up manufacturer technical service bulletins for your specific make and model—some P0379 cases have known factory fixes or require a software update rather than a physical repair.

Inspect the wiring harness and connectors for the high-resolution timing reference circuit. Look for damaged insulation, broken wires, corrosion at the pins, and any signs of connectors that have been pulled apart or not seated fully.

At the sensor connector, use a multimeter to check reference voltage, ground integrity, and signal continuity back to the ECU. Compare your readings to what the manufacturer specifies in the service data.

Perform a wiggle test on the harness while monitoring live data from the sensor. Any dropouts or interruptions during the test point to a broken wire that only fails when moved.

Clear the code, then drive the vehicle through a complete drive cycle that recreates the conditions recorded in the freeze frame. If P0379 does not return, the fault was likely intermittent and the wiring may need closer inspection or replacement.

Repair Options and Costs

Addressing the simplest possibilities first keeps repair costs reasonable. The most common fix is repairing or replacing damaged wiring and connectors, which typically runs $80 to $250 depending on the extent of the damage and labor involved. If the sensor or actuator that generates the timing reference has failed, replacement parts and labor generally cost between $150 and $500. When the problem traces back to the ECU itself, module repair or replacement is the last resort and usually costs $300 to $1,000.

Most independent shops charge $80 to $150 per hour for diagnostic work. Spending time on careful diagnosis before buying parts almost always saves money—the expensive scenario is rarely where you need to start.

Driving Safety Verdict

Severity level: short

P0379 typically allows you to continue driving in most situations, though you may notice reduced power, poor throttle response, or higher fuel consumption. If the car develops stalling, a no-start condition, or any warnings related to braking or steering assist, treat it as urgent and have it towed. Otherwise, schedule diagnosis within a few days rather than ignoring the check engine light indefinitely.

Related OBD2 Codes

• P0300: Random/Multiple Cylinder Misfire Detected
• P0301: Cylinder 1 Misfire Detected
• P0302: Cylinder 2 Misfire Detected
• P0303: Cylinder 3 Misfire Detected
• P0304: Cylinder 4 Misfire Detected
• P0305: Cylinder 5 Misfire Detected