OBD Fuel Control System B Too Lean at Higher Load Bank 1
What it means
P21FC stands for Fuel Control System B Too Lean at Higher Load Bank 1. P21FC is a P code, so the fault sits in the engine, transmission and emissions systems. For P21FC, the second digit places it in fuel and air metering. For P21FC, work through the cause list below, cheapest checks first.
What to check first
For P21FC, check the bank 1 reading against the other bank before buying parts, since if only one side is out of range that side is the fault.
Check these first
- P21FC: Faulty or contaminated sensor in the fuel/air metering circuit
- P21FC: Damaged or shorted wiring or connector for the affected circuit
- P21FC: Vacuum leak or intake system restriction
- P21FC: Failing fuel pump, injector, or fuel pressure regulator
What to do next
P21FC reports from the fuel and air metering system. These steps cover P21FC in general, and the exact cause on your vehicle can differ from the cause named above.
- P21FC: Read freeze frame data and related codes with an OBD-II scanner
- P21FC: Inspect the affected sensor wiring and connector for damage
- P21FC: Compare live sensor readings (fuel trim, airflow, temperatures) to manufacturer specs
- P21FC: Smoke test the intake system if lean or vacuum conditions are suspected
- P21FC: Replace the failed component after confirming it with live data
Look up another code
Enter a full code or a symptom. Press / to search. How to read a code
Type a code above, or start from a symptom or a common code.
Updated
Generic SAE J2012 definition. Last updated 2026-08-30.