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DTC codes / P23xx · Ignition system and misfire / P23F9

P23F9Cylinder 8 Injector B Air-Fuel Ratio Imbalance

P23F9 indicates that the powertrain control module has detected an air-fuel ratio imbalance specifically on cylinder 8, injector B, meaning that cylinder's combustion event is deviating from the fuel trim strategy the computer commands. The module monitors crankshaft speed fluctuations and oxygen sensor feedback to flag this cylinder as either running richer or leaner than the rest of the engine.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaIgnition system and misfire

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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