P20A8Reductant Injection Air Pressure Control Valve 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
- P20A8 says the air pressure control valve's drive circuit sits at too low a level, which normally means a short to ground. Depending on whether the valve is switched on the high or the low side, this either stops the valve from opening at all or energizes it without command. In both cases the controller loses control of the atomizing air. The fault differs from P20A6, where the circuit is interrupted, and from P20A9, a short toward battery voltage. No manufacturer documents P20A8 publicly. For the comparable valves of its air-assisted system, Deutz lists the high-side short to ground as P2060 on the air pump or supply valve and as P1061 on the air switching valve. CARB requires such circuit checks on every electrical component of the SCR system. A chafed harness on the frame rail is the classic finding.
- What you may notice
- MIL or SCR lamp on
- Blown fuse possible on high-side switched valves
- Dosing stopped, derate on trucks
- Likely causes
- LikelyHarness chafed through to ground along the frame
- PossibleSolenoid coil shorted to the valve body
- PossibleWater in the connector creating a path to ground
- 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: €50 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.