Timing Reference High Resolution Signal B Too Few Pulses
Your engine's computer isn't receiving enough timing pulses from the camshaft position sensor, like a metronome that's skipping beats. This prevents the ECU from properly synchronizing fuel injection and spark timing.
The ECU monitors the high-resolution camshaft timing signal (Bank B) to count pulses within a specific crankshaft rotation window. When pulse count falls below the minimum threshold, the ECU detects a signal deficiency and sets this fault. The sensor must deliver consistent pulses at expected intervals for proper cam synchronization.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Camshaft B pulse count per revolution | Expected number of pulses per crankshaft rotation | Fewer pulses detected than minimum threshold |
| Signal frequency stability | Consistent pulse timing within tolerance | Irregular or missing pulses indicating sensor degradation |
Code P0378 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, P0378 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.