Powertrain, generic (extended)

P2A75 Alternative Fuel Hydraulic Pump Pressure Sensor Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

In a hydraulically driven LNG pump system the controller watches the oil pressure delivered by the hydraulic pump. Westport's patent US8726785B2 places this sensor in the supply line between the hydraulic pump outlet and the hydraulic drive, using it for three jobs: reversing the drive at each stroke end, spotting an empty tank when peak pressure stays low, and flagging leaks or other abnormal conditions. Caterpillar's design likewise feeds supply and return pressure to the controller to shift its directional valve. P2A75 is the general circuit fault of this hydraulic pump pressure sensor. Without the signal, the pump cannot be cycled correctly and LNG delivery may stop. No manufacturer publishes P2A75; P2A77 and P2A78 cover low and high.

Likely causes

Connector or harness at the hydraulic pressure sensor damaged
Hydraulic pump pressure sensor faulty
Sensor supply or ground disturbed

Symptoms

  • Check engine light on
  • LNG pump stops or strokes irregularly, gas pressure drops
  • Dual-fuel engine runs on diesel only or with reduced power

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–800
Time1–3 h

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

Parts involved

alt fuel hyd pump pressure sensorwiring harnessafcm

Related codes

P2A76P2A77P2A78P2A79P2A7AP2A70

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