Suzuki FI Code C15: Coolant Temp Sensor — Causes & Fix
On Suzuki motorcycles and scooters, FI code C15 means a fault in the engine coolant temperature (ECT) sensor circuit — used by the ECM for cold-start enrichment and fan control.
- Applies to
- Suzuki motorcycles
- Est. repair cost
- $15 – $95
- Time to fix
- 30–90 minutes
What it means
Check for a loose/corroded connector, low coolant around the sensor, harness damage, or a failed ECT sensor. 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 C15
- Hard cold starts or rough warm-up
- Cooling fan running oddly
How to fix it
- 1
Check the connector and coolant
1. Locate the ECT sensor in the coolant passage. 2. Reseat the connector; make sure coolant is topped up so the sensor stays submerged.
- 2
Test resistance and replace
1. Compare the sensor’s resistance to the temperature chart. 2. Replace it if out of spec, then clear the code.
Frequently asked questions
Can low coolant cause C15?
Yes — if the tip isn’t covered by coolant it reports the wrong temperature. Top up and bleed the system first.
Last updated July 15, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.