P2A9D — Alternative Fuel High Pressure System Small Leak
The AFCM detects a small leak in the high-pressure alternative fuel system based on pressure decay rate after engine shutdown. Common in CNG vehicles where seal aging causes slow gas loss.
General code reference. Confirm the definition and diagnostic procedure for your vehicle's year, model and engine. A stored code alone does not identify a failed part.
Affected components
- Alt fuel high pressure lines
- Alt fuel seals
- Alt fuel tank
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- Seal aged at fitting or valve
- High-pressure fitting loose
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Sources
Check each reference's vehicle and model-year scope. General background links do not establish which fault is most likely on your vehicle.
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.