Code Definition

P0384 — Glow plug preheat control module Circuit high Circuit B

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

About P0384

P0384 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 P0384 is stored, the module has detected a signal or supply voltage lower than the expected operating range; and 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 P0384 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 a high voltage condition in the glow plug preheat control module circuit for Circuit B. This may be caused by an open circuit, high resistance, or a failing control module. Proper operation of the glow plug system is critical for cold starts in diesel engines, and an overvoltage condition can lead to excessive glow plug wear or failure.

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