P21DBCylinder 1 Injector B Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P21DB means the drive circuit of the B injector on cylinder 1 is pulled toward ground. Two makers document it, with opposite meanings of B. Mitsubishi's 2022 Eclipse Cross uses B for the direct high-pressure injector (its port injector faults are P0261 ff.) and sets P21DB when an interruption or a grounded line persists for 2 s with 10 to 16.5 V battery and over 10 V on the injector driver supply. One faulty cylinder loses both its injectors; with several faults direct injection is switched off and the engine runs on port injection with limited torque. GM's 2019 LT5 V8 tests the low side of its supplemental B injector with the driver off: below 0.5 Ohm to ground in 20 of 25 samples, Type A. Ford covers B faults only with P21CF to P21D6, opens and shorts together. P21DC is the high counterpart, P21CF the open circuit.
- What you may notice
- Check engine light on
- Cylinder 1 misfire or shut-off
- Reduced torque when several cylinders are affected (Mitsubishi)
- Likely causes
- LikelyInjector wire chafed through to ground
- PossibleInjector winding open or shorted to its housing
- PossibleDamaged intermediate or injector connector
- RareEngine or injection control module faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.