Yamaha Immobilizer Code 51: Key Not Recognised — Fix
On Yamaha motorcycles and scooters with an immobilizer, code 51 means the immobilizer unit cannot receive a code from the key — it isn’t picking up the transponder chip in the key.
- Applies to
- Yamaha motorcycles
- Est. repair cost
- $0 – $60
- Time to fix
- 20–90 minutes
What it means
Common causes are the wrong/non-transponder key, the key held too far from the ignition, other keys or metal near the ignition interfering, or a faulty antenna coil/wiring around the ignition switch. Yamaha shows immobilizer faults as codes 51–55 on the same diagnostic display used for FI codes, on models fitted with the Yamaha Immobilizer (chip-key) anti-theft system. The engine will not start until the fault is resolved. Once the key/immobilizer fault is resolved the code clears; some faults (key or component registration) require a Yamaha diagnostic tool and the registration procedure.
Symptoms
- Engine won’t start; immobilizer/key warning
- Code 51 shown
- Sometimes intermittent, depending on how the key sits
How to fix it
- 1
Use the correct key and remove interference
1. Use the bike’s original registered (chip) key. 2. Remove other keys, fobs, or metal from the keyring. 3. Hold the key close to the ignition and retry.
- 2
Check the antenna coil and wiring
1. Inspect the antenna coil around the ignition switch and its wiring/connector. 2. Repair or replace if faulty, then clear the code.
Frequently asked questions
Why won’t my Yamaha start with code 51?
The immobilizer can’t read the key’s chip, so it blocks the engine. Use the original registered key and remove other keys/metal from the ring first — that clears most cases.
Last updated July 16, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.