P2A84Alternative Fuel Pump B Compression Stroke Valve Control Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Warning lamp after several drive cycles
- Lower delivery from one tank or element
- Likely causes
- LikelySpool of valve B slow or leaking internally
- PossibleContaminated hydraulic oil
- RareWorn plunger seals on the cryogenic side of pump B
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €200 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.