Code Definition

P0388 — Crankshaft Position Sensor B Circuit High Input

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

About P0388

P0388 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 P0388 is stored, the module has detected a signal or supply voltage higher than the expected operating range; and a sensor-related fault — the reported value from the named sensor is out of spec.

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 P0388 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 engine control module (ECM) sets this code when it detects a voltage signal from the crankshaft position sensor (CKP) 'B' circuit that is higher than the expected range. This can occur due to an open circuit, short to voltage, or an internal sensor fault. The CKP sensor provides critical data for ignition timing and fuel injection, and an abnormal signal can lead to drivability issues.

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