DTC codes / P22xx · Fuel and air metering (injector circuits) / P223A
P223A indicates that the engine control module has detected a fault in the control circuit for the reductant heater, which is the heating element used to keep diesel exhaust fluid (DEF) from freezing in selective catalytic reduction systems. The computer monitors the electrical circuit that commands the heater on and off, and it sets this code when the circuit's voltage or current does not match the expected values for 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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