P20D4Exhaust Aftertreatment Fuel Injector B Control Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- On the second exhaust fuel doser (B), the control line sits at or near battery voltage, so the driver cannot pull it low to open the valve. No manufacturer documents P20D4 publicly. For injector A, GM's diesel tables flag excess current in the switched-on state as a short to power and rate it Type B (P20CE). With doser B out of action, the share of the exhaust it serves no longer gets enough heat for regeneration. CARB requires circuit monitoring for every electronic part of an in-exhaust injection system. For the same doser, P20D1 covers a broken line and P20D3 a grounded one.
- What you may notice
- Check engine light on
- Regeneration impaired, soot load rising
- Likely causes
- LikelyControl wire to doser B shorted to a powered circuit
- PossibleShorted turns in the doser B solenoid
- RareFaulty output stage in the control module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · 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.