What does code P21A9 mean?

Q: What does code P21A9 mean?

Reductant Level Sensor B Circuit Range/Performance. P21A9 indicates that the powertrain control module has detected an out-of-range or performance fault in the reductant level sensor B circuit, which is part of the diesel exhaust fluid system on vehicles equipped with selective catalytic reduction. The computer compares the sensor signal against expected values and sets this code when the voltage or rationality check falls outside the manufacturer's acceptable window.

DTC codes / P21xx · Fuel and air metering / P21A9

P21A9Reductant Level Sensor B Circuit Range/Performance

P21A9 indicates that the powertrain control module has detected an out-of-range or performance fault in the reductant level sensor B circuit, which is part of the diesel exhaust fluid system on vehicles equipped with selective catalytic reduction. The computer compares the sensor signal against expected values and sets this code when the voltage or rationality check falls outside the manufacturer's acceptable window.

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.