A light is located in or beside (depending on year and model) the speedometer assembly to alert the driver to the need for EGR system maintenance.
The device has a mileage sensor to light the visual signal at certain mileage intervals.
Upon completion of the required EGR system maintenance, the warning light can be turned off by resetting the switch. It is in the speedometer cable, on the left side junction of the cable behind the dash, or below it under the instrument panel. To reset the sensor, slide the switch.