What does code P21FB mean?

Q: What does code P21FB mean?

Fuel Control System B Too Rich at Idle (Bank 2). P21FB indicates that the powertrain control module has detected an excessively rich fuel mixture on bank 2 while the engine is idling, meaning the exhaust oxygen content is lower than expected for the commanded air-fuel ratio. The computer monitors short- and long-term fuel trims and sees that it cannot lean out bank 2 enough to reach stoichiometry at idle, so it flags the fault.

DTC codes / P21xx · Fuel and air metering / P21FB

P21FBFuel Control System B Too Rich at Idle (Bank 2)

P21FB indicates that the powertrain control module has detected an excessively rich fuel mixture on bank 2 while the engine is idling, meaning the exhaust oxygen content is lower than expected for the commanded air-fuel ratio. The computer monitors short- and long-term fuel trims and sees that it cannot lean out bank 2 enough to reach stoichiometry at idle, so it flags the fault.

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.