P2A81Alternative Fuel Pump A Compression Stroke 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
- P2A81 is stored when the control circuit of pump A's compression stroke valve sits lower than the commanded state allows. With a low-side driver this mostly points to the control wire touching ground, which can energise the solenoid permanently; with a high-side driver a coil with shorted turns or a grounded feed pulls the output down until its protection trips. A valve held in the fill position keeps oil on the drive side, so the plunger cannot retract and refill, and pump A stays parked at full travel. In Caterpillar's six-element layout the remaining elements may cover part of the demand. No manufacturer publishes P2A81. Disconnect the valve and test the control wire for continuity to chassis ground.
- What you may notice
- Warning lamp on
- Pump A stops delivering, power drops at high load
- Likely causes
- LikelyControl wire of valve A shorted to ground
- PossibleShorted turns in the solenoid coil
- RareWater in the valve connector
- 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.