The Peugeot 406 is a sporty coupe or sedan equipped with a diesel engine. When the engine needs to be serviced, the electronic control unit (ECU), or service light, illuminates on the dashboard. It can easily be reset without the use of any tools and without going to a Peugeot mechanic.
Switch off the ignition.
Hold down the tripmeter button on the dashboard.
Switch on the ignition.
Hold down on the tripmeter button for 10 seconds until the service light turns off and "0" is displayed on the dashboard.