P20D9Exhaust Aftertreatment Fuel Supply 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
- For the fuel supply valve feeding the exhaust doser, the control line reads too low, which points to a short to ground. Volvo and Mack store P20D900 and, in AHI troubleshooting guide KC-2157, group it with the other electrical faults of the AHI module: check the module's connector and wiring harness. Depending on whether the valve is switched on its high or low side, a grounded line can either hold it shut or let it open unasked; most systems then disable dosing to be safe. The open circuit is P20D7 and the short to power P20DA. Valve sticking without an electrical cause is reported separately as P20DB or P20DC.
- What you may notice
- Check engine light on
- Dosing disabled, no active regeneration
- Likely causes
- LikelyChafed wire in the dosing module harness touching ground
- PossibleWater in the dosing module connector
- RareInternal short in the supply valve coil
- 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 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.