P2A3E: Alternative Fuel Delivery Error
What to do
The car will fall back to petrol and keep running. Check the gas gauge first — an empty tank produces this code, and the gauge on a converted system is often less trustworthy than the petrol one. If there is fuel in it, ask when the gas filter was last changed; on a conversion nobody has serviced, that is the usual answer.
What this code means
The gaseous fuel system did not deliver the fuel it was asked for.
"Alternative fuel" in the standard means a gaseous fuel — LPG, autogas or compressed natural gas — and a car running one is carrying a second, largely parallel fuel system.
Most such vehicles are bi-fuel: a full petrol system, and beside it a pressurised tank, its own lines, its own injectors, and a control module of its own. The car starts on petrol and switches to gas once it has warmed up — because the vaporizer that turns liquid gas into vapour is heated by engine coolant, a detail that turns out to matter for diagnosis — and either fuel can run it.
Which produces the diagnostic property that makes this whole range different: the car has a working fallback. A fault that would strand a petrol car merely makes this one switch back and keep going. So the complaint is almost never "it stopped" — it is "it will not run on gas any more", or "it keeps dropping back to petrol", and the driver may have tolerated it for months because the car still works and only the fuel bill changed.
The second consequence is that a gas system is a pressure system, and the parts in this range exist mostly to contain and measure that pressure rather than to meter fuel. That is why the shutoff valves get their own codes and why they are treated as safety devices rather than as plumbing.
This is the system-level outcome code, and it sits above every component code in the range. The module commanded a quantity of gas, watched what the engine did, and concluded it did not arrive.
Which makes the interesting case the one where it stands alone. With a valve or sensor code beside it, this is the consequence. With nothing beside it, every component reports healthy and the fuel still is not arriving — and that points at the things no component code covers: the tank being empty, which sounds trivial and is the single commonest cause; a line restriction; a filter nobody has changed since the conversion was fitted; or a vaporizer not producing gas because it never warmed up.
Gas systems are fitted and then forgotten. They have filters, and those filters have service intervals, and a conversion done by a previous owner rarely comes with a service history. Ask when the gas filter was last changed before diagnosing anything expensive.
Likely causes
Start here
- Empty alternative fuel tank · easy
- Restricted alternative fuel filter · moderate
- Faulty alternative fuel tank shutoff valve · specialist
Less common
- 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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