Suzuki FI Code C31: Gear Position Sensor — Fix
On Suzuki motorcycles and scooters, FI code C31 means a fault in the gear position sensor circuit — the switch that tells the ECM which gear is selected (used for the gear indicator and fuel/ignition maps).
- Applies to
- Suzuki motorcycles
- Est. repair cost
- $20 – $140
- Time to fix
- 30–90 minutes
What it means
Usual causes are a loose/corroded connector, damaged wiring, or a worn gear-position switch. This is a generic Suzuki fuel-injection (FI) code, so it applies across Suzuki FI models — the Raider R150 Fi, Smash, Gixxer, GSX-R and GSX-S range, V-Strom, and more. Suzuki reports it as a "C" number, shown through the FI-light blink pattern or by entering the bike’s dealer/diagnostic mode. After the fault is repaired it becomes a stored "history" code; clear it through Suzuki’s dealer/diagnostic mode so the FI light goes out.
Symptoms
- FI light on with code C31
- Gear indicator blank or wrong
- Minor fuelling/ignition-map effects
How to fix it
- 1
Inspect the connector and wiring
1. Locate the gear position switch on the gearbox. 2. Reseat the connector and check the harness.
- 2
Test and replace
1. Confirm the signal changes with gear selection. 2. Replace the switch if faulty, then clear the code.
Frequently asked questions
Will C31 stop the bike?
Usually not — it mainly affects the gear indicator and small map adjustments. The bike generally still runs, but it’s worth fixing.
Last updated July 16, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.