Ford Aerostar 1986-1997 Repair Guide

Emission Maintenance Warning Light



The emission maintenance warning light system consists of an instrument panel mounted amber lens (with EGR or EMISS printed on it) that is electrically connected to a module located under the instrument panel. The purpose of the system is to alert the driver that emission system maintenance is required. Specific maintenance requirements are listed in the Emission System Scheduled Maintenance Chart.

The system actually measures accumulated vehicle ignition key on-time and is designed to continuously close an electrical circuit to the amber lens after 2000 hours of vehicle operation. Assuming an average vehicle speed of 30 mph, the 2000 hours equates to approximately 60,000 miles (96,000 km) of vehicle operation. Actual vehicle mileage intervals will vary considerably as individual driving habits vary.

Every time the ignition is switched ON , the warning light will glow for 2-5 seconds as a bulb check and to verify that the system is operating properly. When approximately 60,000 miles (96,000 km) is reached, the warning light will remain on continuously to indicate that service is required. After the required maintenance is performed, the module must be reset for another 60,000 (96,000 km) mile period. The module is located under the dashboard, on a bracket below the EEC-IV computer.


  1. Make sure the ignition key is in the OFF position.
  3. Locate the sensor under the dashboard, on a bracket below the EEC-IV computer, and lightly push a Phillips screwdriver or equivalent through the 0.2 in. (5mm) diameter hole with the sticker labeled "RESET" and lightly press down and hold.
  5. While lightly holding the screwdriver down, turn the ignition switch to the RUN position. The emission warning light will then light and should remain on for as long as the screwdriver is held down. Hold the screwdriver down for approximately five seconds.
  7. Remove the screwdriver. The lamp should go out within 2-5 seconds, indicating that a reset has occurred. If the light remains on, begin again at Step 1. If the light goes out, turn the ignition OFF and go to the next step.
  9. Turn the ignition to the RUN position. The warning light should illuminate for 2-5 seconds and then go out. This verifies that a proper reset of the module has been accomplished. If the light remains on, repeat the reset procedure.