What it means
The alternative fuel tank select valve C control circuit signal is lower 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 is controlled through an electrical circuit monitored by the module. This code sets when the valve C circuit signal falls below the expected level, which can result from a wire shorted to ground, a shorted valve coil, or corroded connector contacts.
Common causes
Most likely first.
- Control wire shorted to ground
- Internal short in 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
- Review freeze-frame and live data to establish whether valve C was commanded when its circuit signal went low.
- Inspect valve C’s harness for rubbed insulation or a section contacting ground, and check its connector for corrosion.
- Check valve C connector pins for looseness or corrosion that could add resistance and reduce the monitored signal.
- Test the isolated valve C control wire for a short to ground and check the coil for an internal short, following the wiring diagram.
- Compare results with the manufacturer’s specification to identify whether the wire, connector, or valve is responsible.
Common fixes
- Clean and secure corroded or loose valve C connector pins.
- Repair the valve C control wire if it is shorted to ground.
- Replace valve C if the coil is internally shorted.
- Clear the code and verify the valve C circuit during a tank-switch command.
Can I keep driving?
The low circuit signal may stop valve C from switching tanks, with possible power loss or stalling. Avoid driving if the engine runs poorly, and do not count on changing tanks until the fault is corrected.
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.