What it means
The alternative fuel tank select valve A control circuit is open or has a fault.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
Alternative fuel tank select valve A directs fuel from the selected tank into the system. The control module monitors the valve A control circuit and sets P2A91 when it detects an open or circuit fault that can prevent the valve from switching as commanded.
Common causes
Most likely first.
- Open in valve control wire
- Open valve coil
- Pin pushed back out of connector body
Symptoms
- Check-engine or alternative-fuel system warning light, if equipped
- Difficulty switching fuel tanks
- Loss of power or stalling
How to diagnose it
- Record freeze-frame data and check whether the fault appeared during a tank-switch command or alongside fuel-system warnings.
- Inspect valve A's connector for a pushed-back pin, corrosion, looseness, or damaged seals.
- Trace valve A's control wiring for breaks, chafing, or disconnected sections between the valve and control module.
- With the circuit isolated as specified by the manufacturer, check valve A's coil and wiring continuity for an open.
- If the open is not at the valve, test circuit continuity through the harness to the control module using the vehicle wiring diagram.
Common fixes
- Reseat the connector pin that has pushed back and secure the connector.
- Repair an open or damaged section of valve A's control wire.
- Clean or replace a corroded connector terminal and restore a sound connection.
- Replace valve A if its coil is open and the wiring and connector are intact.
Can I keep driving?
Avoid switching tanks while driving if the vehicle cannot reliably select a fuel source, and stop safely if it loses power or stalls. A failed selection can leave the engine without a usable fuel supply.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.