Suzuki FI Code C29: Secondary Throttle Position Sensor — Fix
On Suzuki motorcycles and scooters, FI code C29 means a fault in the secondary throttle position (STP) sensor circuit — the sensor that reports the position of the secondary throttle valves.
- Applies to
- Suzuki motorcycles
- Est. repair cost
- $20 – $150
- Time to fix
- 30–90 minutes
What it means
Common causes are a loose/corroded connector, a worn sensor, 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 C29
- Soft or uneven power delivery
- Hesitation at partial throttle
How to fix it
- 1
Inspect the connector and wiring
1. Locate the STP sensor on the throttle body. 2. Reseat the connector and check the harness.
- 2
Check the sweep and replace
1. Verify the sensor output tracks the secondary valves smoothly. 2. Replace if faulty, then clear the code.
Frequently asked questions
Is C29 related to C28?
Yes — both involve the secondary throttle system. C29 is the position sensor; C28 is the actuator that moves the valves.
Last updated July 16, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.