P2A88: Alternative Fuel Pump C Compression Stroke Valve Control Circuit Range/Performance
What to do
The car will fall back to petrol, or run on gas with reduced power under load. This is a liquid-injection gas system — less common than the usual vapour type, and it needs an installer who works on them specifically.
What this code means
The control circuit for the compression stroke valve on gaseous fuel pump C is faulty.
A compression stroke valve tells you this pump is a positive-displacement design, and that changes what its faults mean.
An ordinary electric fuel pump spins continuously and produces whatever pressure the restriction downstream creates. A positive-displacement pump instead moves a measured slug of fuel on each stroke, and a valve controls when the compression stroke happens. So the pump does not produce pressure — it produces volume, on command, and the pressure follows.
Which is why the timing of that valve is a fuelling input rather than a plumbing detail. The module decides when to compress, and a valve that does not respond on cue does not simply reduce flow: it delivers at the wrong moment, which on a liquid-injection system means fuel arriving at a pressure that has not yet been established.
Three pumps means a system built for volume — a large engine, or a commercial installation running several tanks. Losing one is a partial failure, so the car keeps working with less capacity, and the complaint is reduced power on gas under sustained load rather than anything abrupt.
The liquid-injection background is at P2A70, and it matters here: this hardware only exists on systems that keep the fuel liquid all the way to the injector.
The circuit is electrically sound and the part did not do what it was told. That points at the mechanism rather than the wiring.
Likely causes
Start here
- Faulty alternative fuel hydraulic pump · specialist
- Corroded or loose connector · specialist
Less common
- Open circuit in control wiring · specialist
- Control module driver failure · specialist
- Damaged wiring harness · specialist
Symptoms
Components involved
Information, not instruction
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Community experience
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