Powertrain, generic (extended)

P240D Alternative Fuel Low Pressure System Leak

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P240D applies only to vehicles running on a gaseous alternative fuel such as CNG or LPG, which CARB counts as alternate-fueled. It indicates a leak in the low-pressure part of the gas system, downstream of the pressure regulator. GM's bulletin PI1330 for the 2015 Impala bi-fuel shows this layout: the regulator reduces tank pressure to 68-130 psi, a low-pressure cut-off solenoid feeds a filter and oil separator and then the gas rail, and a relief valve caps that side at 290 psi if it is opened. How P240D is detected is not published by any manufacturer; a plausible approach is watching how pressure behaves with the shut-off valves closed. P240E is the matching code for the high-pressure side. A gas leak is a safety issue: stop using the gas system and have it inspected.

Likely causes

Leaking fitting or hose on the regulated low-pressure side
Leaking seal at the low-pressure filter or oil separator housing
Gas rail or gas injector seal leaking

Symptoms

  • Check engine light, gas mode may be disabled
  • Gas smell in the engine bay
  • Higher gas consumption

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–800
Time1–3 h

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

Parts involved

alternative fuel low pressure linealternative fuel shutoff valve

Related codes

P240EP0093P01A5

References: law.cornell.edu, static.nhtsa.gov, en.wikipedia.org.