What does code P21F9 mean?

Q: What does code P21F9 mean?

Fuel Control System B Too Rich at Idle (Bank 1). P21F9 means the powertrain control module (PCM) has detected that the fuel control system for bank 1 is delivering a mixture that is too rich at idle, based on oxygen sensor feedback showing excess fuel or insufficient oxygen in the exhaust. The PCM has exceeded its calibrated threshold for rich correction at idle, meaning the engine is receiving more fuel than the closed-loop fuel control can compensate for.

DTC codes / P21xx · Fuel and air metering / P21F9

P21F9Fuel Control System B Too Rich at Idle (Bank 1)

P21F9 means the powertrain control module (PCM) has detected that the fuel control system for bank 1 is delivering a mixture that is too rich at idle, based on oxygen sensor feedback showing excess fuel or insufficient oxygen in the exhaust. The PCM has exceeded its calibrated threshold for rich correction at idle, meaning the engine is receiving more fuel than the closed-loop fuel control can compensate for.

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.