Powertrain, generic (extended)

P2A84 Alternative Fuel Pump B Compression Stroke Valve Control Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2A84 is set when pump B's compression stroke valve is electrically sound yet the pump does not respond as commanded. A controller that drives several pumps or elements in turn can compare them: in Caterpillar's multi-element patent, flow results from how often the elements are fired and how long each waits, so an element adding less pressure per command than its neighbours stands out. A slow spool, contaminated oil, internal leakage past the spool or worn plunger seals on the cryogenic side can all reduce pump B's output. With two tank pumps as in Westport's patent, the pressure behaviour before and after a switchover can also be compared. No manufacturer publishes P2A84. Check oil condition and compare delivery with pump A.

Likely causes

Spool of valve B slow or leaking internally
Contaminated hydraulic oil
Worn plunger seals on the cryogenic side of pump B

Symptoms

  • Warning lamp after several drive cycles
  • Lower delivery from one tank or element

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€200–2,500
Time1.5–6 h

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

Parts involved

alt fuel pump b compression stroke valvewiring harnessafcm

Related codes

P2A83P2A85P2A86P2A80P2A88

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