Cause
Faulty alternative fuel tank select valve
The valve that chooses which gaseous fuel tank is feeding the engine has failed or stuck.
Conversions frequently carry more than one tank — a toroidal tank in the spare wheel well plus a cylinder in the load space is a common pairing — because a single tank of usable size gives poor range next to petrol. The select valve makes them behave as one supply, and the module switches between them as they empty.
Which is why a stuck select valve does not stop the car. It strands fuel. The system draws one tank down, cannot switch, and reports itself out of gas with half its capacity still full.
That produces a complaint nobody traces back to a valve. The owner reports that range has suddenly halved, which sounds like a leak, a consumption problem, or a tired conversion. The free check that settles it is the refill quantity: if the car now takes roughly half the gas it used to at the pump, the fuel is not being consumed faster — it is not being reached.
Two practical notes. The letter in the code identifies the valve, not the tank, and on an aftermarket installation only the installer's documentation maps either to a physical location. And a valve that is electrically sound but mechanically stuck reports as a performance fault rather than a circuit one — no wiring test will find it.
Typically specialist work. Needs equipment or training most home workshops do not have.
Codes this can cause (12)
Codes where this is a likely explanation first, rather than merely a possible one.
- P2A91 Alternative Fuel Tank Select Valve A Control Circuit/Open Likely for this code Moderate
- P2A92 Alternative Fuel Tank Select Valve A Control Performance Likely for this code Moderate
- P2A93 Alternative Fuel Tank Select Valve A Control Circuit Low Likely for this code Moderate
- P2A94 Alternative Fuel Tank Select Valve A Control Circuit High Likely for this code Moderate
- P2A95 Alternative Fuel Tank Select Valve B Control Circuit/Open Likely for this code Moderate
- P2A96 Alternative Fuel Tank Select Valve B Control Circuit Performance Likely for this code Moderate
- P2A97 Alternative Fuel Tank Select Valve B Control Circuit Low Likely for this code Moderate
- P2A98 Alternative Fuel Tank Select Valve B Control Circuit High Likely for this code Moderate
- P2A99 Alternative Fuel Tank Select Valve C Control Circuit/Open Likely for this code Moderate
- P2A9A Alternative Fuel Tank Select Valve C Control Circuit Performance Likely for this code Moderate
- P2A9B Alternative Fuel Tank Select Valve C Control Circuit Low Likely for this code Moderate
- P2A9C Alternative Fuel Tank Select Valve C Control Circuit High Likely for this code Moderate
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.
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