Powertrain, generic (extended)

P2A70 Alternative Fuel Hydraulic Fuel Pump Select Valve Control Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Some heavy-duty LNG systems do not drive the cryogenic tank pump directly but through hydraulics: an engine- or motor-driven hydraulic pump supplies oil to a reciprocating hydraulic drive on each tank pump. Westport's patent US8726785B2 shows two LNG vessels whose pumps sit inside the tanks, plus a selector valve that the controller switches to decide which pump receives hydraulic flow. P2A70 covers the electrical control circuit of such a select valve and is set when the driver output detects a general fault. If the valve cannot be commanded, the system may be stuck on one tank or lose LNG supply. No manufacturer publishes P2A70; CARB's heavy-duty rule requires output components to be monitored. P2A72 and P2A73 separate the low and high cases.

Likely causes

Damaged harness or connector at the select valve on the frame
Select valve solenoid coil faulty
Output stage in the controlling module faulty

Symptoms

  • Check engine light on
  • Fuel drawn from one LNG tank only, range reduced
  • Loss of gas supply, dual-fuel engine falls back to diesel-only or derates

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

P2A71P2A72P2A73P2A74P2A75

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