What it means
Fuel mode switch input reads stuck low — short to ground or stuck-closed contact. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
The fuel-mode select switch sends an electrical input that the control module uses to identify a driver's fuel request. This code sets when that input stays below its expected range, commonly because the signal wire is shorted to ground or the switch contact is stuck closed.
Common causes
Most likely first.
- Switch wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check-engine light may come on
- Fuel-mode indicator may be absent or incorrect
- Vehicle may remain on one fuel or fail to switch fuels
How to diagnose it
- Record freeze-frame data and observe the fuel-mode switch input on a scan tool to confirm that it remains low despite operating the switch.
- Inspect the switch connector and harness for chafing, water ingress, corrosion, and pushed-back pins.
- With the circuit safely isolated as specified by the vehicle maker, disconnect the switch and see whether the scan-tool input changes.
- Check the signal wire for a short to ground and inspect connector terminals for high resistance or poor contact.
- Test the switch and circuit continuity against the manufacturer's specification to locate the low input.
Common fixes
- Repair insulation where the fuel-mode switch signal wire is shorted to ground.
- Clean or repair corroded, loose, or pushed-back connector terminals.
- Replace a switch that remains closed when it should change state.
- Repair the harness routing where it is chafing against another part.
Can I keep driving?
If the vehicle runs normally on its default fuel, drive gently and assume fuel-mode changes may be unavailable. Avoid a trip that depends on switching fuels, and stop if the engine starts to stumble or lose power.
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.