DTC codes / P23xx · Ignition system and misfire / P23C9
P23C9 indicates that the fuel heater control module has detected a high-voltage condition on its power control circuit, meaning the circuit voltage is above the expected range when the heater is commanded on or off. The engine control module (ECM) or fuel heater control module monitors this circuit and sets the code when the signal exceeds a calibrated threshold, typically indicating a short to voltage or an open circuit in the ground path.
Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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