What it means
Fuel mode switch input reads stuck high — short to battery voltage. 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 its state to the control module through a monitored electrical circuit. This code sets when the input stays above its expected range, often because the signal wire is shorted to battery voltage or the harness is contacting a powered supply.
Common causes
Most likely first.
- Switch wire shorted to battery voltage
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
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 watch the fuel-mode switch input on a scan tool to confirm that it stays high while the switch is operated.
- Inspect the switch connector and harness for pinched insulation, chafing near powered wiring, water ingress, and pushed-back pins.
- With the circuit safely isolated as specified by the vehicle maker, disconnect the switch and check whether the input returns to its normal state.
- Test the signal wire for an unwanted connection to battery voltage and inspect terminals for corrosion or poor contact.
- Test the switch and circuit against the manufacturer's specification to distinguish a switch fault from a harness short.
Common fixes
- Repair the signal wire where it contacts a battery-voltage supply.
- Restore damaged or pinched harness insulation and secure the wiring away from powered components.
- Clean or repair corroded, loose, or pushed-back connector terminals.
- Replace a faulty fuel-mode select switch if circuit tests rule out a wiring short.
Can I keep driving?
If the vehicle runs normally on its default fuel, drive gently and assume fuel-mode changes may be unavailable. Avoid relying on a changeover, and stop if the engine stumbles or loses 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.