DTC codes / P23xx · Ignition system and misfire / P23D4
P23D4 indicates that the powertrain control module (PCM) has detected a performance fault in the fuel heater circuit for cylinder 1, meaning the heater is not raising fuel temperature as expected or the circuit response is outside the calibrated range. The PCM monitors the heater's electrical current and temperature rise during cold-start or low-temperature operation, and it sets this code when the measured performance does not match the commanded state.
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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