System: Powertrain (P-Code)
SAE Standard (Generic)
Family: Alternative Fuel Pressure Leak
Code P240D: Alternative Fuel Low Pressure System Leak
Diagnostic & Technical Explanation
Code P240D (Alternative Fuel Low Pressure System Leak) sets when the CNG/LPG fuel control module's pressure-decay test finds the compressed gas supply losing pressure faster than the calibrated leak threshold on either the low-pressure regulated side or the high-pressure tank side of the system. Because the fuel is stored under high pressure, causes are a leaking high-pressure fitting, a failing tank valve seal, or a cracked regulator diaphragm, and any of these requires the vehicle's gas-system depressurization procedure before repair.
First-listed procedure
Rank #1
Repair high-pressure fitting leak
Professional Required
This is the first procedure in the authored
consideration order, not a measured cause likelihood. Execute it only when its prerequisites
and diagnostic findings support it. Its cost and labor estimates (where known), the step-by-step procedure and the
remaining 3 procedure(s) are in the licensed dataset. Ordering context.
Full family: Alternative Fuel Pressure Leak
What this page does not show
This page publishes the fault mechanism and the code index. The licensed dataset adds, for
every one of the 15,886 codes, the full authored repair set (56,729 procedures in total)
with the fields deliberately withheld here:
- Procedures 2..n after the first-listed procedure
- Aftermarket parts cost ranges in USD (
est_parts_cost_min/max_usd)
- Professional labor-hour estimates (
est_labor_hours)
- Step-by-step diagnostic and repair instructions
- Replacement-part mappings and catalog lookups
- 6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)