Timing Reference High Resolution Signal B Too Many Pulses
The engine's timing sensor is sending too many pulses to the computer, like a heartbeat monitor reading double the actual beats. This usually means the sensor is faulty, the wiring is damaged, or there's an electrical short.
The ECU monitors the Camshaft Position Sensor B (high-resolution signal) to track timing pulses per crankshaft rotation. It expects a specific pulse count range within each cycle. Excessive pulses indicate sensor noise, electromagnetic interference, or a malfunctioning sensor.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Pulses per rotation | Expected count per spec (typically 58-62 teeth) | Exceeds maximum threshold by >10% |
| Signal frequency | Steady pattern matching engine RPM | Erratic spikes or doubled signal rate |
Code P0377 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0377 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.