Suzuki FI Code C42: Ignition Switch Signal — Fix
On Suzuki motorcycles and scooters, FI code C42 means a fault in the ignition switch signal to the ECM — often linked to the ignition/immobilizer circuit.
- Applies to
- Suzuki motorcycles
- Est. repair cost
- $30 – $300
- Time to fix
- 30–90 minutes
What it means
Common causes are a faulty ignition switch, an immobilizer/antenna fault, or wiring/connector problems. 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 C42
- No start or intermittent starting
- Immobilizer warning on some models
How to fix it
- 1
Check the ignition switch and wiring
1. Inspect the ignition switch connector and wiring. 2. Confirm the switch passes the correct signal to the ECM.
- 2
Diagnose the immobilizer
1. On immobilizer-equipped models, have the immobilizer/antenna checked with the proper tool. 2. Repair and clear the code.
Frequently asked questions
Is C42 an immobilizer problem?
It can be — on models with an immobilizer, a key/antenna or ignition-switch fault can trigger C42 and block starting. It often needs dealer-level diagnosis.
Last updated July 16, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.