DTC codes / P23xx · Ignition system and misfire / P23B4
P23B4 indicates that the engine control module has detected an implausible signal from the heater sense circuit of the third nitrogen oxide (NOx) sensor on bank 1. The sensor's internal heater is not drawing the current the module expects, so the circuit is flagged as faulty.
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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