P2A7E: Alternative Fuel Hydraulic Pressure Sensor Circuit Intermittent/Erratic
What to do
The car will switch to petrol unpredictably and you will not be able to reproduce it on demand. That is the system being cautious rather than broken. The sensor connector is the usual cause.
What this code means
The system hydraulic pressure sensor circuit is intermittent.
A hydraulic fuel pump on a gas system means this is a liquid injection installation, which is a different and more sophisticated thing from the vapour systems the rest of this range describes.
Ordinary LPG conversions vaporise the fuel and inject it as a gas into the inlet manifold. That works, and it costs a little power — gas displaces air, so the engine breathes less of it. Liquid injection keeps the fuel liquid all the way to the injector and sprays it into the port, which recovers that power and actually cools the incoming charge as it flashes to vapour.
The price is that liquid LPG must be kept above its boiling point pressure the whole way, or it vaporises in the line and the injectors deliver nothing. That is what the hydraulic pump is for — it raises tank pressure by several bar so the fuel stays liquid regardless of temperature.
And it is why this hardware has its own pressure sensors and its own select valves. The system has to know it is maintaining that margin continuously, because losing it does not degrade fuelling gradually — the fuel flashes to vapour and delivery collapses at once, usually under sustained load on a hot day, which is exactly when nobody wants it.
These are less common installations, mostly factory or high-end aftermarket, and they need an installer familiar with liquid systems specifically. A workshop used to vapour conversions may not recognise the hardware.
Intermittent is the worst variant on a liquid system, because the pressure margin it protects is not something the car can be cautious about. A reading that drops out momentarily looks identical to a genuine loss of pressure, so the system stops using gas as a precaution and does it unpredictably — a car that switches to petrol at random and cannot be made to repeat it on demand.
Found by moving the harness with the reading live, not by measuring at rest.
A note on the title. Both sources spell this
Intermitttent, with three t's. Because the second source spells the corpus's other four known dataset typos correctly, the error is most likely in the standard itself rather than in either transcription — the corpus writesIntermittent/Erratic, matching every one of its siblings.
Likely causes
Start here
- Corroded or loose connector · specialist
- Intermittent wiring fault · specialist
- Faulty alternative fuel pressure sensor · specialist
Less common
- Damaged wiring harness · specialist
- Heat damage to sensor or wiring · 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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