P2A4E: Alternative Fuel Temperature Sensor Circuit High
What to do
Expect worse economy on gas, and possibly a car that runs noticeably differently in hot or cold weather. It will fall back to petrol if the system gives up. Mention whether the problem is seasonal — that detail points straight here.
What this code means
The circuit for the gaseous fuel temperature sensor is faulty.
Gas has to be measured by temperature as well as pressure, and the reason is that the injectors meter volume while the engine needs mass.
Pressure alone does not say how much fuel is in a given volume of vapour. The same pressure at 0 °C and at 60 °C carries substantially different mass, and it is mass that burns. So the module reads pressure and temperature together, and calculates from both — which is why losing either one produces the same symptom.
In practice this sensor is what keeps a gas conversion running correctly across the seasons, and its failure shows up as a car that was fine in spring and runs badly in high summer, or the reverse. A fault that tracks the weather is pointing here, and it is a pattern nobody reports as a pattern because the two events are months apart.
It is usually combined with the pressure sensor in one housing on the rail, so a fault in one often means the other is about to follow, and replacing the assembly settles both.
At or above the upper limit, usually an open circuit.
Likely causes
Start here
- Faulty fuel temperature sensor · specialist
- Corroded or loose connector · specialist
- Open circuit in sensor wiring · specialist
Less common
- Damaged wiring harness · specialist
- Failed sensor reference voltage supply · 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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