Ford Ranger/Bronco II 1983-1990 Repair Guide

Emission Maintenance Warning Light


See Figure 1

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Fig. Fig. 1: Emission maintenance light system schematic

The emission maintenance warning light system (starting 1985 model year) consists of an instrument panel mounted amber lens (with EGR or EMISS printed on it that is electrically connected to a sensor 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 Charts. Note for your vehicle use these charts as a guide for recommended service.

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 1 mph, the 2000 hours equates to approximately 60,000 miles 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 25 seconds as a bulb check and to verify that the system is operating properly. When approximately 60,000 miles is reached, the warning light will remain on continuously to indicate that service is required. After the required maintenance is performed, the sensor must be reset for another 60,000 mile period. The sensor module is located above the right front corner of the glove box assembly.


  1. Make sure the ignition key is OFF .
  3. Locate the sensor (above the right front corner of the glove box), and lightly push a Phillips screwdriver or small rod tool 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 or tool 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 5 seconds.
  7. Remove the screwdriver or tool. The lamp should go out within 25 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 25 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.

Some models (Non-EEC 2.0L engine) use a non-resettable control unit. When reset has occurred, replace it with a resettable type if available.