What does code P21B3 mean?

Q: What does code P21B3 mean?

Closed Loop NOx Adsorber Control At Limit - Too High. P21B3 means the engine computer has commanded the closed-loop nitrogen oxide (NOx) adsorber control to its maximum correction limit, yet the exhaust sensor still reports NOx reduction performance outside the expected range. The powertrain control module (PCM) detected that the adsorber system cannot achieve the required NOx storage or regeneration even at full authority, indicating a fault in the adsorber, its control circuit, or the feedback sensor.

DTC codes / P21xx · Fuel and air metering / P21B3

P21B3Closed Loop NOx Adsorber Control At Limit - Too High

P21B3 means the engine computer has commanded the closed-loop nitrogen oxide (NOx) adsorber control to its maximum correction limit, yet the exhaust sensor still reports NOx reduction performance outside the expected range. The powertrain control module (PCM) detected that the adsorber system cannot achieve the required NOx storage or regeneration even at full authority, indicating a fault in the adsorber, its control circuit, or the feedback sensor.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

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.