P2A9D: Alternative Fuel High Pressure System Small Leak
What to do
Switch the car to petrol and stay on petrol. The system has detected fuel escaping slowly — small enough that you may smell nothing, which is exactly what makes it worth acting on. LPG is heavier than air and pools in low enclosed spaces, so avoid parking in a garage or over a pit until it has been tested. This needs a gas installer, not a general workshop.
What this code means
The gaseous fuel system has detected a small leak on its high pressure side.
This is the code in the range that matters most, and it is worth being plain about why a small leak is the serious one.
A large gas leak announces itself. It smells — the stenchant added to LPG exists precisely so a leak is obvious — and it usually produces a running fault the driver cannot miss. A small leak does neither. It can persist for months, and the only thing that notices is the system watching pressure decay while the car is parked.
And LPG is heavier than air, which is what makes a slow leak different in kind from a petrol weep. It does not disperse upward; it pools in the lowest enclosed space it can reach — a garage floor, an inspection pit, the footwell of a car parked on a slope. That is why gas installations are required to be vented to the outside, and why a leak inside the vehicle envelope is treated as urgent even when the quantity is small.
How the test works is worth knowing, because it explains a code that appears overnight with no symptom. The system closes the tank valve and watches whether pressure holds. A slow decay with everything shut means fuel is escaping somewhere between the tank valve and the injectors — a fitting, a line that has chafed against the underbody, or an injector not sealing (P2A40).
Do not clear it and continue on gas. Switch to petrol, leave it there, and have the system pressure-tested by a gas installer.
Likely causes
Start here
- Leaking alternative fuel line or fitting · specialist
- Leaking alternative fuel injector · specialist
Less common
- Faulty alternative fuel tank shutoff valve · specialist
- Faulty alternative fuel pressure sensor · specialist
Rare
- Corroded or loose connector · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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