P2A72: Alternative Fuel Hydraulic Fuel Pump Select Valve Control Circuit Low

P2A72 is set when the control circuit of the hydraulic fuel pump select valve reads lower than expected for the commanded state. On a low-side driver this typically means the control wire is shorted to ground, so the valve coil may stay energised; on a high-side driver a short to ground or a shorted coil pulls the output down and may trip its protection. Either way the controller can no longer trust which LNG tank pump is being driven. Westport's patented system relies on knowing the valve position to assign hydraulic pressure readings to the right pump, so tank selection and empty-tank detection become unreliable. No manufacturer documents P2A72. Measure coil resistance and check the harness for chafing against the chassis.

High severity. Can I keep driving?If you smell gas, do not keep driving or start the engine: move away and call for assistance. With no smell, drive moderately to an authorized shop.

Symptoms

Check engine light on
Select valve stays switched, one tank pump runs permanently
Gas supply interrupted when the active tank runs empty

Most likely causes

Control wire chafed on the frame and shorted to ground
Select valve coil with shorted turns
Water in the connector bridging to ground

What to check, in order

Start with the simplest. You can tick off each step.

If you smell gas, shut off the supply, ventilate and do not start the engine
With the connector unplugged, check whether the signal wire is making contact with ground.
Read the codes with a compatible scanner
Check the connectors and wiring of the component indicated
Leave any work on the gas circuit to an authorized shop

Good to know

Repair difficulty: hard
It can trigger limp mode.
It affects emissions.

What each character of P2A72 means

P: Powertrain: engine and transmission
2: Generic code: same on every make
A: Hybrid or air and fuel
72: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2A72?

If you smell gas, do not keep driving or start the engine: move away and call for assistance. With no smell, drive moderately to an authorized shop.

What causes code P2A72?

The most common causes are: control wire chafed on the frame and shorted to ground; select valve coil with shorted turns; water in the connector bridging to ground.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.