What does code P21B2 mean?

Q: What does code P21B2 mean?

Excessive Time To Enter Closed Loop NOx Adsorber Control. P21B2 means the engine computer (ECM) commanded the selective catalytic reduction (SCR) system to enter closed-loop nitrogen oxide (NOx) adsorber control, but the system did not respond within the expected time window. The ECM monitors the NOx sensor feedback and the adsorber's ability to store and release NOx, and it sets this code when the transition to closed-loop control is excessively delayed.

DTC codes / P21xx · Fuel and air metering / P21B2

P21B2Excessive Time To Enter Closed Loop NOx Adsorber Control

P21B2 means the engine computer (ECM) commanded the selective catalytic reduction (SCR) system to enter closed-loop nitrogen oxide (NOx) adsorber control, but the system did not respond within the expected time window. The ECM monitors the NOx sensor feedback and the adsorber's ability to store and release NOx, and it sets this code when the transition to closed-loop control is excessively delayed.

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.