Code Definition

P0377 — Timing Reference High Resolution Signal B Too Few Pulses

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

About P0377

P0377 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 P0377 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 P0377 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 insufficient number of pulses from the high-resolution timing reference signal 'B', typically generated by a secondary crankshaft or camshaft position sensor. This issue may be caused by a missing or damaged reluctor wheel tooth, sensor misalignment, or an intermittent signal. A reduced pulse count can lead to poor engine performance, misfires, hard starting, or stalling.

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