Powertrain, generic (extended)

P2A72 Alternative Fuel Hydraulic Fuel Pump Select Valve Control Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2A72 is set when the control circuit of the hydraulic fuel pump select valve reads lower than expected for the commanded state. On a low-side driver this typically means the control wire is shorted to ground, so the valve coil may stay energised; on a high-side driver a short to ground or a shorted coil pulls the output down and may trip its protection. Either way the controller can no longer trust which LNG tank pump is being driven. Westport's patented system relies on knowing the valve position to assign hydraulic pressure readings to the right pump, so tank selection and empty-tank detection become unreliable. No manufacturer documents P2A72. Measure coil resistance and check the harness for chafing against the chassis.

Likely causes

Control wire chafed on the frame and shorted to ground
Select valve coil with shorted turns
Water in the connector bridging to ground

Symptoms

  • Check engine light on
  • Select valve stays switched, one tank pump runs permanently
  • Gas supply interrupted when the active tank runs empty

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–1,200
Time1–4 h

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

Parts involved

alt fuel hyd pump select valvewiring harnessafcm

Related codes

P2A70P2A71P2A73P2A74

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