Suzuki FI Code C28: Secondary Throttle Valve Actuator — Fix
On Suzuki motorcycles and scooters, FI code C28 means a fault in the secondary throttle valve actuator (STVA) — the motor that moves the ECM-controlled secondary throttle plates.
- Applies to
- Suzuki motorcycles
- Est. repair cost
- $40 – $300
- Time to fix
- 30–90 minutes
What it means
Usual causes are a seized or failed actuator motor, a loose/corroded connector, or damaged wiring. 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 C28
- Reduced or soft power delivery
- No actuator "self-check" movement at key-on
How to fix it
- 1
Inspect the actuator connector and wiring
1. Locate the STVA on the throttle body. 2. Reseat the connector and check the harness.
- 2
Test and replace
1. Confirm the actuator moves the valves freely (no binding). 2. Replace if seized or unresponsive, then clear the code.
Frequently asked questions
Why is my Suzuki down on power with C28?
The ECM holds the secondary throttles in a safe position when the actuator faults, softening power until it’s repaired.
Last updated July 16, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.