OBD-II code · Powertrain (generic, extended)
P21F5 Fuel Control System B Too Rich Off Idle (Bank 1)
Fuel Control System B Too Rich Off Idle (Bank 1): the fuel-trim control is correcting for an over-rich mixture in this operating range.
Is it safe to drive with P21F5?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyPort injectors leaking
- PossibleFuel pressure high
Symptoms
- Check engine light on
- Increased fuel consumption
- Black smoke from exhaust on acceleration
- Smell of unburned fuel, fouled spark plugs
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.7–4 h
- Emissions test
- Likely to fail
- Parts involved
- Fuel Injector, Fuel Pressure Regulator, Oxygen Sensor
Related codes
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.