Powertrain, generic (extended)

P2A8C Alternative Fuel Vaporizer B Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2A8C flags vaporizer B as underperforming: the gas leaving it is colder, or less completely vaporized, than the module expects for the current flow. With LNG the temperature gap is extreme, and Westport's patent CA2862664C describes the typical failure. At a cold start, at idle or under light load coolant crawls through the exchanger and can freeze inside it; flow then drops without stopping entirely, vaporizer capacity falls and the downstream gas temperature sinks, which can harm later components. Westport therefore runs fuel and coolant in parallel flow during start and idle and switches to counter flow afterwards. A stuck switching valve or ice can thus cause P2A8C. No manufacturer publishes the code or its limits.

Likely causes

Coolant partly frozen inside vaporizer B after cold start or long idling
Valve that switches between parallel and counter flow stuck
Low coolant level or too little antifreeze in the mixture
Deposits reducing heat transfer in vaporizer B

Symptoms

  • Malfunction lamp on
  • Reduced power or gas mode blocked, especially when cold
  • Ice on the vaporizer or gas lines behind it

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€150–2,500
Time1–5 h

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

Parts involved

alt fuel vaporizer bengine coolant circuitafcm

Related codes

P2A8BP2A8DP2A55P2A56

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