What it means
The control circuit of alternative fuel tank shutoff valve C reports a control circuit high condition. Tank isolation cannot be commanded as expected on multi-tank CNG/LPG systems.
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
In a multi-tank CNG or LPG system, shutoff valve C controls whether its tank can be isolated. The control module monitors the valve C circuit and detects when its signal is higher than expected. A wire shorted to battery voltage, an open coil, or a poor connector can cause this high-circuit fault.
Common causes
Most likely first.
- Control wire shorted to B+
- Open valve coil
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Alternative-fuel warning light
- Difficulty switching fuel modes
How to diagnose it
- Record freeze-frame data and check with a scan tool whether the fault returns when valve C is commanded.
- Inspect valve C's connector and harness for corrosion, loose or pushed-back terminals, and wiring chafed against a power source.
- With the system disabled according to the manufacturer's procedure, check the valve C control wire for a short to battery voltage.
- Test valve C's coil and circuit continuity against the manufacturer's specification to identify an open coil or connection.
- If the valve and wiring pass, check the control-module output using the vehicle's approved procedure.
Common fixes
- Clean and secure corroded or loose valve C connector terminals.
- Repair the control wire shorted to battery voltage.
- Replace valve C if its coil is open.
- Repair the control-module circuit if testing confirms an output fault.
Can I keep driving?
Do not count on valve C to isolate its tank or on fuel-mode switching to work normally until the fault is resolved. Follow the vehicle's fuel-system warnings and avoid using alternative fuel if the system reports that it is unavailable.
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.