What it means
The alternative fuel tank select valve C 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 C receives electrical commands through its control circuit. The module monitors the circuit while operating the valve; this code sets when the signal is higher than expected, such as from a short to battery voltage, an open coil, or poor connector 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 to confirm the circuit fault occurred during a valve C command and note any failed tank selection.
- Inspect valve C wiring for a short against a battery-positive feed and examine the connector for corrosion or loose pins.
- Verify the valve C connector is fully seated and its pins make sound contact.
- Use the wiring diagram to test the coil for an open and the control wire for a short to battery voltage.
- Compare measurements with the manufacturer’s specification to isolate the wire, connector, or valve fault.
Common fixes
- Clean and secure corroded or loose valve C connector pins.
- Repair the control wire if it is shorted to battery voltage.
- Replace valve C if its coil is open.
- Clear the code and confirm valve C responds correctly to a commanded switch.
Can I keep driving?
Valve C may fail to switch tanks, potentially causing power loss or stalling. Avoid driving if the vehicle is losing power or running roughly, and do not rely on tank selection until 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.