DTC codes / P21xx · Fuel and air metering / P21A0
P21A0 indicates that the powertrain control module has detected an air-fuel ratio imbalance on cylinder 5, meaning that cylinder's combustion is not matching the fuel and air delivered to the other cylinders. The computer monitors crankshaft speed fluctuations and oxygen sensor feedback to flag this specific cylinder as deviating from the expected balance.
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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