Powertrain, generic (extended)

P2CDA Alternative Fuel Tank A Vacuum Insulation Deteriorated

Check engine lightUsually off
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2CDA concerns cryogenic fuel storage, in practice liquefied natural gas (LNG) and possibly liquid hydrogen, kept in a double-walled tank whose gap is evacuated. Once that vacuum softens, heat leaks in, the liquid boils faster and pressure climbs until the relief valve vents gas. Chart, a maker of LNG truck tanks, separates true vacuum loss from other causes by an eight-hour pressure rise test combined with an outer shell that feels cold or shows condensation. A Caterpillar patent lets the ECM compare pressure at key-off and key-on against a predicted rise and rate hold time, with under one day flagged as poor. No manufacturer documents this code publicly. The tank pressure sensor codes start at P019E. Expect shorter standing times before venting and lost fuel.

Likely causes

Vacuum between inner and outer tank wall lost through a leaking weld, fitting or seal
Gradual vacuum decay from outgassing over years of service, tank due for pump-down
Dent or impact damage to the outer shell breaching the insulation space
Pressure rise from another cause (economizer, pressure regulator, sensor) misread as insulation loss

Symptoms

  • Tank pressure rises quickly while the vehicle stands, relief valve vents gas
  • Frost or condensation on the outer tank shell
  • Fuel loss and shorter standing time after refuelling

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€500–8,000
Time2–16 h

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

Parts involved

alt fuel tank aalt fuel tank a insulation

Related codes

P019EP019FP01AAP2BB2P224C

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