P2A40: Alternative Fuel System - Injector Leakage to Rail Detected
What to do
Switch the car to petrol and stay on petrol until this is fixed. A leaking gas injector fills the inlet manifold while the car is parked, and the usual result is a hard backfire on start-up that can damage the airbox — or worse. If it has already backfired on starting, say so. Take it to a gas installer, not a general workshop.
What this code means
Gas is leaking past an injector into the fuel rail when it should not be.
This is the code in the range with a genuine safety edge, and the mechanism is worth being plain about.
A gas injector that does not seal lets fuel through while the engine is stopped. On a petrol system a weeping injector floods a cylinder — bad, expensive, but contained. On a gas system the leak is a vapour that fills the inlet manifold and then, given time, anything the manifold connects to. Gaseous fuels are heavier than air in the case of LPG, so they pool rather than disperse, and an engine bay is not a ventilated space.
The consequence an owner meets is a car that backfires through the inlet on starting, sometimes violently enough to split an air hose or crack the airbox — because the manifold has filled with an ignitable mixture while the car sat overnight.
So this is not a code to run with. The system detected the leak, which is the safety design working. Switch to petrol and leave it there until it is repaired, and mention any backfiring on start-up, because that is the symptom that says the leak is already large enough to matter.
Likely causes
Start here
- Leaking alternative fuel injector · specialist
- Fuel contamination · moderate
Less common
- Restricted alternative fuel filter · moderate
Rare
- Failed alternative fuel control module · specialist
- 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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