Code Definition

P0378 — Timing Reference High Resolution Signal B Intermittent/Erratic Pulses

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0378

P0378 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0378 is stored, the module has detected a signal or supply voltage higher than the expected operating range.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0378 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The powertrain control module (PCM) sets this code when it detects an intermittent or erratic signal from the high-resolution timing reference signal 'B', which is typically generated by a secondary crankshaft or camshaft position sensor. This can be caused by inconsistent sensor readings due to wiring issues, sensor failure, or mechanical faults in the reluctor wheel. An unstable timing signal can lead to rough idling, misfires, hesitation, or even engine stalling.

Quick Facts