Powertrain, generic (extended)

P2A81 Alternative Fuel Pump A Compression Stroke Valve Control Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Control wire of valve A shorted to ground
Shorted turns in the solenoid coil
Water in the valve connector

Symptoms

  • Warning lamp on
  • Pump A stops delivering, power drops at high load

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–1,500
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

alt fuel pump a compression stroke valvewiring harnessafcm

Related codes

P2A7FP2A80P2A82P2A85P2A89

References: law.cornell.edu, patents.google.com.