What it means
The disable feedback signal sits below its valid window. Usually a short to ground or an open pull-up that lets the input float low.
At a glance
- Usually lights the check-engine light
How it works
The alternative-fuel disable signal circuit returns feedback that confirms the disable command was carried out. This code sets when the control module sees feedback voltage below its valid range, which can be caused by a grounded wire or a failed input pull-up that leaves the signal low.
Common causes
Most likely first.
- Feedback wire shorted to ground
- Open pull-up resistor in the controller input
- Connector pins corroded - high contact resistance
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 record freeze-frame data and check the disable feedback value against the command status.
- Inspect the feedback wire and connectors for crushed or chafed insulation that could let the signal touch ground.
- Check relay and module connector pins for corrosion, looseness, or poor contact.
- With the circuit isolated as specified by the manufacturer, test the feedback wire for a short to ground and check its continuity.
- If the wiring is sound, follow the manufacturer's procedure to check the module's feedback input pull-up.
Common fixes
- Repair feedback wiring shorted to ground.
- Clean or repair corroded or loose connector terminals.
- Repair a broken or damaged feedback wire.
- Replace or repair the control module if its input pull-up is confirmed faulty.
Can I keep driving?
The system may not be able to confirm that alternative fuel has been disabled, and the engine may switch to or remain on the other fuel. Avoid depending on alternative-fuel operation until checked, and stop if there is fuel leakage or unsafe engine behavior.
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.