OBD-II code · Powertrain (generic, extended)
P21F3 Cylinder 12 Injector B Circuit High
Cylinder 12 second-injector (B) drive line stuck high — short to B+. A flow-deviating injector throws off cylinder balance — adjacent cylinders run leaner/richer to compensate, often masking the root cause until the trim limit is hit.
Is it safe to drive with P21F3?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyShort to B+
- Less likelyConnector pins corroded - high contact resistance
- Less likelySupply wire pinched against B+ source
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–4 h
- Emissions test
- Likely to fail
- Parts involved
- Fuel Injector
Related codes
- P21DACylinder 12 Injector B Circuit/Open
- P21DCCylinder 1 Injector B Circuit High
- P21DFCylinder 2 Injector B Circuit High
- P21E1Cylinder 3 Injector B Circuit High
- P21E3Cylinder 4 Injector B Circuit High
- P21E5Cylinder 5 Injector B Circuit High
- P21E7Cylinder 6 Injector B Circuit High
- P21E9Cylinder 7 Injector B Circuit High
- P21EBCylinder 8 Injector B Circuit High
- P21EDCylinder 9 Injector B Circuit High
- P21EFCylinder 10 Injector B Circuit High
- P21F1Cylinder 11 Injector B Circuit High
- P21F0Cylinder 11 Injector B Circuit Low
- P21F2Cylinder 12 Injector B Circuit Low
- P21F4Fuel Control System B Too Lean Off Idle (Bank 1)
- P21F5Fuel Control System B Too Rich Off Idle (Bank 1)
- P21F6Fuel Control System B Too Lean Off Idle (Bank 2)
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.