P21F2 code meaning
Cylinder 12 Injector B Circuit Low
Powertrain system Generic code P21xx codes Check engine light
What P21F2 means
P21F2 is the generic code for a low circuit state, usually a grounded control wire, at the B injector of cylinder 12. It would need a twelve-cylinder engine with two injectors per cylinder, and none could be documented: the V12s from Lamborghini and Aston Martin inject into the ports only. No manufacturer publishes the code in this sense. One maker does use the number differently: McLaren bulletin KA-01931 lists P21F205 and P21F22F on the Artura, a V6 plug-in hybrid, as high-voltage battery faults (safety design current too low/high), repaired by replacing battery parts. On an Artura it is therefore a battery fault, not an injector fault. For a genuine injector fault, CARB's circuit monitoring applies, and GM's V8 criteria (ground short below 0.5 Ohm) are a guide. High fault: P21F3.
P21F2 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyHard
- Typical labor1 to 5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P21F2
- Check engine light on
- Misfire on cylinder 12 (P0312)
- Hybrid warning instead, if the code is a McLaren battery fault
Common causes of P21F2
- Most likelyCylinder 12 B injector wire shorted to ground
- PossibleInjector with internal ground fault
- Less likelyManufacturer-specific use of the number (McLaren Artura high-voltage battery)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injectorInjector wiringEngine control module
What each part of P21F2 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. |
| F2 | The exact fault in that area. |
What to do next
- Note P21F2 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 P21F2
What does P21F2 mean?
P21F2 means "Cylinder 12 Injector B Circuit Low". P21F2 is the generic code for a low circuit state, usually a grounded control wire, at the B injector of cylinder 12. It is a generic code, so it means the same on every make.
Is it safe to drive with P21F2?
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 P21F2 fail an emissions test?
Yes, it can. P21F2 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 P21F2 to fix?
Difficulty: hard. A typical repair takes 1 to 5 hours of work. This is a job for a workshop.
Will P21F2 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.