P21F6 code meaning
Fuel Control System B Too Lean Off Idle (Bank 2)
Powertrain system Generic code P21xx codes Check engine light
What P21F6 means
P21F6 is the bank 2 form of P21F4 and only exists on V or flat engines whose cylinder banks each have their own front oxygen sensor and two injection paths. Here the part-load correction of the second path on bank 2 has reached its lean limit. No manufacturer documents this code publicly. Ford, whose 5.0 Coyote V8 gained direct injection on top of port injection for 2018, reports a lean port-injection fault on bank 2 as P2BF2 instead, without load zones, once long-term trim exceeds 25 % together with short-term trim above 1 % for 2 s. CARB demands a fault once adaptive control has used up its permitted range. If bank 1 stays clean, look at bank 2 alone: a clogged port injector or a wiring fault on that bank's injector harness.
P21F6 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 3.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P21F6
- Check engine lamp on
- Slight hesitation at part load
Common causes of P21F6
- PossibleRestricted port injector on bank 2
- PossibleWiring or connector fault on the bank 2 injector harness
- Less likelyLow pressure in the shared port fuel rail (if bank 1 also lean)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injectorOxygen sensor
What each part of P21F6 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 1 | Area: fuel and air metering. |
| F6 | The exact fault in that area. |
What to do next
- Note P21F6 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P21F6
What does P21F6 mean?
P21F6 means "Fuel Control System B Too Lean Off Idle (Bank 2)". P21F6 is the bank 2 form of P21F4 and only exists on V or flat engines whose cylinder banks each have their own front oxygen sensor and two injection paths. It is a generic code, so it means the same on every make.
Is it safe to drive with P21F6?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P21F6 fail an emissions test?
Yes, it can. P21F6 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P21F6 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3.5 hours of work. This is a job for a workshop.
Will P21F6 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.