What does code P21B5 mean?

Q: What does code P21B5 mean?

NOx Adsorber Over Temperature (Bank 2). P21B5 means the engine computer has calculated that the nitrogen oxide (NOx) adsorber in Bank 2 has exceeded its safe operating temperature, typically based on exhaust temperature sensors and the NOx sensor feedback. The powertrain control module (PCM) sets this code when the modelled or measured adsorber temperature stays above the calibrated threshold for a set time, protecting the catalyst from thermal damage.

DTC codes / P21xx · Fuel and air metering / P21B5

P21B5NOx Adsorber Over Temperature (Bank 2)

P21B5 means the engine computer has calculated that the nitrogen oxide (NOx) adsorber in Bank 2 has exceeded its safe operating temperature, typically based on exhaust temperature sensors and the NOx sensor feedback. The powertrain control module (PCM) sets this code when the modelled or measured adsorber temperature stays above the calibrated threshold for a set time, protecting the catalyst from thermal damage.

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.