P2A76 Alternative Fuel Hydraulic Pump Pressure Sensor Range/Performance

P2A76 is set when the hydraulic pump pressure reading looks electrically sound yet makes no sense for the operating state. Westport's patent explains why a fixed expectation is not enough: pressure rises with hydraulic pump speed, which follows engine speed when the pump is engine-driven, and with the LNG pressure the cryogenic pump works against. The controller therefore corrects its thresholds with a look-up table. A reading that stays flat while the pump strokes, shows no drop at stroke end, or disagrees with downstream fuel pressure points to a drifting sensor, but also to worn pump seals or low oil level. No manufacturer publishes P2A76 or its limits. Compare with a mechanical gauge on the test port and check the oil level.

Likely causes

Symptoms

• Check engine light on
• Uneven LNG pressure or slow pressure build-up
• Empty-tank warning although LNG remains

Repair estimate

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

Parts involved

Related codes

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