What does code P21AD mean?

Q: What does code P21AD mean?

Reductant Level Sensor C Circuit. P21AD indicates that the powertrain control module (PCM) has detected an electrical fault in the signal circuit for the reductant level sensor C, which is part of the diesel exhaust fluid (DEF) system on vehicles equipped with selective catalytic reduction (SCR). The PCM monitors the sensor's voltage or resistance and sets this code when the reading falls outside the expected range for the current operating conditions, often due to an open, short, or erratic connection.

DTC codes / P21xx · Fuel and air metering / P21AD

P21ADReductant Level Sensor C Circuit

P21AD indicates that the powertrain control module (PCM) has detected an electrical fault in the signal circuit for the reductant level sensor C, which is part of the diesel exhaust fluid (DEF) system on vehicles equipped with selective catalytic reduction (SCR). The PCM monitors the sensor's voltage or resistance and sets this code when the reading falls outside the expected range for the current operating conditions, often due to an open, short, or erratic connection.

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.