P2AA0Alternative Fuel Return Line Valve 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
- P2AA0 means the module reads too low a voltage on the control line of the return line valve, which almost always points to a short to ground. What follows depends on which side the module switches. In the ROUSH CleanTech Gen 4 propane layout the valve has a fused battery feed and its ground wire runs to a relay module; if that ground wire chafes against the frame, the coil is energized whenever the supply is live and the valve can no longer be closed. With a high-side driver the same short would instead blow the fuse or make the driver shut down. No manufacturer documents P2AA0 publicly, and CARB only requires that such output faults be detected. Check the harness along the tank and frame first, then the coil.
- What you may notice
- Malfunction indicator lamp on
- Return valve stays open or the valve fuse blows, depending on the circuit layout
- Irregular rail pressure or switch to the base fuel
- Likely causes
- LikelyControl wire chafed through and touching the frame or tank
- PossibleWater in the valve connector bridging to ground
- PossibleInternal short in the solenoid coil
- RareDamaged output stage in the fuel 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: €40 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.