Powertrain, generic (extended)

P2A73 Alternative Fuel Hydraulic Fuel Pump Select Valve Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2A73 signals that the select valve control circuit sits at a higher voltage than the commanded state allows. Typical faults are an open coil or broken wire on a low-side driven valve, which leaves the line at supply voltage, or a short to battery voltage that the output cannot pull down. The valve then stays in its spring-return position, so hydraulic flow keeps going to one tank pump whatever the command. On a multi-tank LNG truck the second tank may never be used, and the engine runs short of gas although LNG remains on board. Caterpillar's patent shows such a valve shifted by an actuator under controller command. No manufacturer publishes P2A73. Check coil resistance, the connector and the supply wire.

Likely causes

Valve coil or control wire open
Control wire shorted to battery voltage
Corroded connector pins with very high resistance

Symptoms

  • Check engine light on
  • Second LNG tank not used, range clearly shorter
  • Gas supply stops although fuel remains

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

P2A70P2A71P2A72P2A74

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