Yamaha Error Code 24: O2 Sensor: No Normal Signal

The ECU is not getting a normal signal from the oxygen (O2) sensor in the exhaust, so it cannot fine-tune the fuel mixture. Only models with an O2 sensor use this code.

Low risk

The bike normally keeps running, though fuel economy and smoothness can suffer. Have it checked soon rather than riding on it for weeks.

What causes Yamaha error code 24

CommonLoose or poor contact at the O2 sensor connector
CommonFailed O2 sensor
PossibleAftermarket exhaust fitted without the sensor or with it disconnected
RareDamaged wiring between the sensor and the ECU

How to check and fix it

Start at the top: the most likely and usually cheapest checks come first.

Loose or poor contact at the O2 sensor connector. Find the sensor wire coming from the exhaust pipe, unplug its connector, check the pins and reconnect it firmly. Make sure the wire is not touching the hot exhaust.
Failed O2 sensor. If the connector and wiring are fine and the code returns, replace the sensor with the correct part for your model. Sensors can fail with age even on low-mileage bikes.
Aftermarket exhaust fitted without the sensor or with it disconnected. If the code appeared after an exhaust change, check that the sensor is fitted to the new pipe and plugged in.
Damaged wiring between the sensor and the ECU. Look for melted or chafed insulation near the exhaust and check each wire for continuity to the ECU connector.

Parts & tools you may need

O2 sensor socket
Anti-seize compound

FAQ

Will clearing the code fix it?

Clearing the code only turns the light off. If the sensor or its connection is still faulty, the code will come back.

How do I read code 24 from a flashing check engine light?

Many Yamaha models that flash their codes show tens as long (slow) flashes and ones as short (fast) flashes, which would make this code two long flashes followed by four short (fast) flashes. Patterns can differ between models, so check the information for your bike.

Sources

Last updated: October 7, 2026