What does code P21F4 mean?

Q: What does code P21F4 mean?

Fuel Control System B Too Lean Off Idle (Bank 1). P21F4 indicates that the engine computer has detected an excessively lean air-fuel mixture on Bank 1 while the engine is running above idle, based on fuel trim and oxygen sensor feedback. The powertrain control module (PCM) commands a richer mixture to compensate, but the fuel control system cannot achieve the target, so it sets this code.

DTC codes / P21xx · Fuel and air metering / P21F4

P21F4Fuel Control System B Too Lean Off Idle (Bank 1)

P21F4 indicates that the engine computer has detected an excessively lean air-fuel mixture on Bank 1 while the engine is running above idle, based on fuel trim and oxygen sensor feedback. The powertrain control module (PCM) commands a richer mixture to compensate, but the fuel control system cannot achieve the target, so it sets this code.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

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.