What does code P21A7 mean?

Q: What does code P21A7 mean?

Cylinder 12 Air-Fuel Ratio Imbalance. P21A7 indicates that the powertrain control module (PCM) has detected an air-fuel ratio imbalance on cylinder 12, meaning that cylinder's combustion is deviating from the target ratio compared to the rest of the engine. The PCM monitors crankshaft speed fluctuations and/or oxygen sensor feedback to identify which cylinder is not contributing equally, and it sets this code when the imbalance exceeds a calibrated threshold.

DTC codes / P21xx · Fuel and air metering / P21A7

P21A7Cylinder 12 Air-Fuel Ratio Imbalance

P21A7 indicates that the powertrain control module (PCM) has detected an air-fuel ratio imbalance on cylinder 12, meaning that cylinder's combustion is deviating from the target ratio compared to the rest of the engine. The PCM monitors crankshaft speed fluctuations and/or oxygen sensor feedback to identify which cylinder is not contributing equally, and it sets this code when the imbalance exceeds a calibrated threshold.

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.