P2A86Alternative Fuel Pump B Compression Stroke Valve Control Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2A86 is stored when pump B's compression stroke valve circuit shows a higher voltage than its state allows, pointing to an interrupted coil, a broken return wire where the valve is switched on the ground side, or a short to the supply. The valve then rests in its drain position: drive oil bypasses pump B and its plunger stays retracted. On a two-tank layout as in Westport's patent, the controller may keep drawing from the other tank, so the truck runs on while the second tank's LNG cannot be used and slowly warms up. Because the pump performs no strokes, its usual hydraulic pressure signature disappears, which helps to confirm the diagnosis. No manufacturer documents P2A86. Check the coil, the plug and the supply feed.
- What you may notice
- Warning lamp on
- One LNG tank is no longer emptied
- Shorter range on gas
- Likely causes
- LikelyOpen coil or broken wire at valve B
- PossibleControl wire shorted to supply voltage
- RareCorroded terminals in the valve B plug
- 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: €150 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.