Mazda Trucks 1987-1993 Repair Guide

Emission Maintenance Warning Light


The emission maintenance warning light system consists of an instrument panel mounted amber lens 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.

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 (48 kph), the 2000 hours equates to approximately 60,000 miles (96,500 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 (96,500 km) 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 (96,500 km) period. The sensor module is located above the right front corner of the glove box assembly.


1987-88 Models
  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 inch (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 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.

1989-93 Models


See Figures 1 and 2

On Federal and Canadian vehicles, the Malfunction Indicator Light (MIL) will come on at 60,000-80,000 mile (96,500-128,700 km) intervals to indicate the need for scheduled maintenance of the emission control system.

Click image to see an enlarged view

Fig. Fig. 1: The MIL reset connectors are located under the dashboard, near the realay box

Click image to see an enlarged view

Fig. Fig. 2: At the recommended mileage, switch the reset connectors

On California vehicles, the MIL will come on any time an engine management input device malfunctions, indicating that service is necessary.

After the required service or maintenance has been performed, the MIL can be reset by changing the connector connections.


See Figure 3

Federal and Canadian vehicles are equipped with a mileage sensor which is linked to the odometer. At every 80,000 miles (128,744 km), the mileage sensor will cause the Malfunction Indicator Light (MIL) to illuminate, indicating that the oxygen sensor must be replaced.

Click image to see an enlarged view

Fig. Fig. 3: After replacing the oxygen sensor, remove the instrument gauge cluster assembly and, on the back, reset the MIL by reversing the set screw position

After replacing the oxygen sensor, remove the instrument cluster and reset the MIL by reversing the position of the MIL set screw.


All vehicles are equipped with a "CHECK ENGINE'' or warning light located on the instrument cluster. This light should come on briefly when the ignition key is turned ON , but should turn off when the engine starts. If the light does not come ON when the ignition key is turned ON or if it comes ON and stays ON when the engine is running, there is a malfunction in the electronic engine control system. After the malfunction has been remedied, using the proper procedures, the "CHECK ENGINE'' light will go out.