P2A49: Alternative Fuel Tank C Pressure Sensor Circuit High
What to do
The car will run on petrol, or on gas with worse economy. A gas system running lean can damage valve seats over time, so this is worth fixing rather than tuning around. Use an installer who works on these systems.
What this code means
The circuit for the pressure sensor on gaseous fuel tank C is faulty.
Tank pressure on a gas system is not a fuel-level reading, and confusing the two is the mistake this family invites.
LPG in a tank is a liquid with vapour above it, and the pressure of that vapour is set almost entirely by temperature rather than by how much is left. A tank that is nearly empty and one that is nearly full read close to the same pressure at the same temperature — and the same tank reads perhaps 4 bar on a winter morning and 10 bar after a summer afternoon parked in the sun.
So the module needs this reading for two quite different jobs. It is how the system knows what pressure the gas will arrive at, which changes how long the injectors must be held open for a given quantity of fuel. And it is how the system detects a leak — a tank whose pressure falls when the temperature has not is losing its contents.
Level is measured separately (P2A5F), which is why both exist.
A pressure sensor that reads wrong therefore mis-fuels the engine rather than mis-reporting the gauge. Reading high, the module under-delivers and the engine runs lean, which on gas means high combustion temperatures and, over time, damaged valve seats. That is the expensive failure mode of a cheap sensor, and it is why a lean-running gas conversion is worth taking seriously rather than tuning around.
At or above the upper limit.
Likely causes
Start here
- Faulty fuel tank pressure 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
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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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