What does code P21AB mean?

Q: What does code P21AB mean?

Reductant Level Sensor B Circuit High. P21AB indicates that the powertrain control module (PCM) has detected an abnormally high voltage on the signal circuit for reductant level sensor B, which is the sensor that monitors the diesel exhaust fluid (DEF) level in the storage tank. The PCM interprets this high voltage as an open circuit, a short to voltage, or a sensor internal failure, and it will typically disable the DEF dosing system and may derate engine power.

DTC codes / P21xx · Fuel and air metering / P21AB

P21ABReductant Level Sensor B Circuit High

P21AB indicates that the powertrain control module (PCM) has detected an abnormally high voltage on the signal circuit for reductant level sensor B, which is the sensor that monitors the diesel exhaust fluid (DEF) level in the storage tank. The PCM interprets this high voltage as an open circuit, a short to voltage, or a sensor internal failure, and it will typically disable the DEF dosing system and may derate engine power.

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.