P2A91Alternative Fuel Tank Select Valve 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
- A tank select valve decides which storage vessel feeds the fuel system. That sets it apart from a tank shutoff valve (P224C, P2A22 and onward), which simply opens or isolates one cylinder, and from the hydraulic fuel pump select valve (P2A70 and onward), which routes drive oil to a pump. Westport's patent US8726785B2 shows the idea with two LNG vessels and one external pump, where an insulated valve links the pump to either vessel. P2A91 means the control circuit of select valve A is open or otherwise faulty, so the valve stays in its rest position. Fuel is then drawn only from the vessel reached in that position and the rest may become unusable. No manufacturer documents P2A91 publicly; CARB requires output circuits to be checked for continuity.
- What you may notice
- Malfunction lamp on
- Only one tank is used, range noticeably shorter
- Fuel gauge shows content left although the engine runs short of gas
- Likely causes
- LikelyLoose connector or broken wire to select valve A
- PossibleBurnt-out solenoid coil of valve A
- RareFaulty output stage in the alternative fuel module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · 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.