P0376
Timing Reference High Resolution Signal B Too Many Pulses
When a vehicle powertrain module registers the fault code P0376, it points directly to an internal system malfunction identified as "Timing Reference High Resolution Signal B Too Many Pulses". Operating your engine under this condition may degrade long-term fuel maps.
Driver's Summary
The diagnostic trouble code P0376 indicates an active fault in the timing reference high resolution signal b too many pulses circuit or component. Drivers typically experience erratic idle, surging, stalling when this code is active. Stop driving as soon as it is safe to do so. This fault can lead to expensive secondary damage if left unaddressed.
Symptoms
Erratic idle, surging, stalling
Common Causes
- Electromagnetic interference
- Faulty optical sensor B
- Debris on the sensor reader
- Bad ground connection
How to Fix
- 1 Check routing of ignition wires
- 2 Replace optical sensor B
- 3 Clean sensor components
- 4 Secure ground connections
Technical Explanation
Detection of P0376 occurs when the ECM cross-references multiple sensor inputs and determines that the reported values are physically inconsistent or out-of-range. 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. The fault remains stored in memory even after the MIL is cleared; it becomes a confirmed DTC after failing two consecutive drive cycles, and the PCM logs a freeze frame record of the engine's exact operating state at the moment of detection.
Is It Safe to Drive?
With P0376 active, your engine or transmission is not operating within design parameters. Short-term driving may seem fine, but internal damage is accumulating — particularly to electromagnetic interference.
Mechanic's Pro Tip
The most common mistake with P0376 is replacing the sensor without verifying the reference voltage and ground integrity first. Use a scan tool to monitor the sensor's live output; a truly failed sensor shows a stuck, flatlined reading — a sensor that fluctuates but reads slightly off usually indicates a wiring or vacuum issue, not a dead sensor. Always spray electrical contact cleaner on the connector pins before condemning the sensor.
Sensor cleaning: 100; Replacement: 200 - 400