P20CDExhaust Aftertreatment Fuel Injector A Control 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
- Here the control line of the hydrocarbon doser has a short to ground. GM's diesel tables 18OBDG04 and 25OBDG04A test the output while the driver is off: if the voltage drops below about 2 V, the line is touching ground. GM rates it Type A, which lights the MIL after one trip, and the fault only clears after a calibrated count of good tests or a control-module reset. The LML/LGH Duramax lists it as Type B. A grounded line can make the doser open whenever its supply side is switched on, so fuel may enter the exhaust uncontrolled; that is why it is treated more strictly than the open circuit (P20CB) or the short to power (P20CE).
- What you may notice
- Check engine light on after a single trip
- Doser disabled, no active regeneration
- Possible fuel smell or smoke from the exhaust
- Likely causes
- LikelyControl wire chafed through against the frame or exhaust
- PossibleWater or salt in the doser connector bridging to ground
- RareInternal short in the doser solenoid
- 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.