What it means
The controller cannot drive the alternative-fuel disable line that switches a bi-fuel vehicle (CNG, LPG, hydrogen) back to gasoline. An open detected on the control side blocks the safety shutoff for the gas system.
At a glance
- Usually lights the check-engine light
How it works
The alternative-fuel disable circuit allows the controller to command a bi-fuel vehicle away from CNG, LPG, hydrogen, or another alternate fuel so its safety shutoff can operate. This code sets when the controller detects an open in the disable control circuit, preventing the expected command from reaching the relay or fuel system.
Common causes
Most likely first.
- Broken wire or corroded connector on the disable control line
- Open coil in the alt-fuel disable relay
- Output driver in the alt-fuel control module faulty
Symptoms
- Alternative-fuel operation may be unavailable
- Engine may switch to or remain on the other fuel
How to diagnose it
- Use a scan tool to check for related alternative-fuel codes and confirm which fuel mode the controller reports when the fault is present.
- Check whether the vehicle can switch to its other fuel and whether any alternative-fuel warning or safety alert is active.
- Inspect the disable-control relay, its connector, and the wiring between the controller and relay for loose connections, corrosion, or broken wires.
- Using the wiring diagram and manufacturer’s procedure, check circuit continuity and test the relay coil for an open circuit.
- If wiring and relay tests pass, test the alternative-fuel control module’s output and connector for an open or failed driver.
Common fixes
- Reconnect or repair a loose or broken wire in the alternative-fuel disable control circuit.
- Clean or replace corroded terminals at the relay or controller connector.
- Replace the disable relay if its coil is open on testing.
- Repair or replace the alternative-fuel controller output circuit if testing confirms an internal fault.
Can I keep driving?
Alternative-fuel operation or the ability to switch fuels may be affected, so follow the vehicle’s fuel-system warnings and use only a fuel mode the vehicle confirms is available. If a gas leak or fuel-system warning is present, stop in a safe place and follow the vehicle’s emergency instructions.
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.