What does code P21AF mean?

Q: What does code P21AF mean?

Reductant Level Sensor C Circuit Low. P21AF means the engine control module has detected a low-voltage condition on the signal circuit from the reductant level sensor, which is the sensor that reports how much diesel exhaust fluid remains in the tank. The computer expects a voltage within a specific range and sees the circuit pulled below that threshold, so it flags the sensor circuit as low.

DTC codes / P21xx · Fuel and air metering / P21AF

P21AFReductant Level Sensor C Circuit Low

P21AF means the engine control module has detected a low-voltage condition on the signal circuit from the reductant level sensor, which is the sensor that reports how much diesel exhaust fluid remains in the tank. The computer expects a voltage within a specific range and sees the circuit pulled below that threshold, so it flags the sensor circuit as low.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.