P20CBExhaust Aftertreatment Fuel Injector A Control Circuit/Open
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- The engine computer checks the drive line of the hydrocarbon doser, a separate valve that sprays diesel into the exhaust ahead of the oxidation catalyst so the particulate filter can be heated for regeneration. This code means an open circuit: GM's diesel tables 18OBDG04 and 25OBDG04A watch the voltage on the switched-off driver output and flag a reading stuck in a mid band of roughly 2 to 3 V (Type B, MIL after two trips); the 6.6 L Duramax LML/LGH (15OBDG09) compares commanded and actual driver state. Short to ground and short to power have their own codes (P20CD, P20CE). Some makers use P2697 for the same injector instead. Without the doser the engine cannot finish active regenerations, so soot builds up.
- What you may notice
- Check engine light on
- Particulate filter regeneration does not start or is aborted
- Soot load warning and, later, reduced engine power
- Likely causes
- LikelyCorroded or loose connector at the doser, which sits under the vehicle in the exhaust area
- PossibleHeat- or chafe-damaged wire between engine computer and doser
- PossibleOpen solenoid winding inside the doser
- RareFaulty output stage in the engine 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.