What it means
The alternative fuel tank select valve B control circuit signal is higher than expected.
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 B receives commands through its control circuit. The module monitors the circuit during operation; this code sets when the signal is higher than expected, often because the control wire is shorted to battery voltage, the valve B coil is open, or a connector has poor contact.
Common causes
Most likely first.
- Control wire shorted to B+
- Open valve coil
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine or alternative-fuel system warning light, if equipped
- Difficulty switching fuel tanks
- Loss of power or stalling
How to diagnose it
- Check freeze-frame and live data for the conditions when valve B was commanded and whether the system reported a failed tank switch.
- Inspect valve B’s harness for damage or contact with a battery-positive wire, and look for corrosion or loose connector pins.
- Check the connector seating and pin condition, since poor contact can interrupt the circuit response.
- Following the wiring diagram, test the valve B coil for an open and the control wire for a short to battery voltage.
- Compare measurements with the manufacturer’s specification before deciding whether the fault is in the wire, connector, or valve.
Common fixes
- Repair or clean valve B connector pins and restore a secure connection.
- Repair the control wire if it is shorted to battery voltage.
- Replace valve B if its coil is open.
- Clear the code and verify valve B operation with a commanded tank switch.
Can I keep driving?
Valve B may not switch tanks, which can cause reduced power or stalling. Avoid driving if the engine runs erratically or loses power, and do not depend on switching tanks until the circuit is repaired.
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.