Timer Unit: Description and Operation

This article has been updated by Techincal Service Bulletin 89228 dated November 1989.

The Combination IMS/EMW module is located at the bottom of the instrument panel left of the steering column.

There are three types of emission maintenance warning modules specified in the vehicles covered by the Technical Service Bulletin:

The Emission Maintenance Warning "EMW" module operates a light that is located on the instrument panel.
- For 1985-87 model year vehicles, the light will display the word "EMISSIONS".
- For 1988-89 model year vehicles, the light will display the words "CHECK ENGINE".
When the light is lit, it is indicating that the 60,000 mile emission maintenance should be performed.
After the maintenance is performed the EMW module must be reset to zero time. Service and Repair

Another type of module is the "IMS" module.
This module is not part of the light circuit and does not require maintenance.
At a predetermined time, the IMS module directs the EEC IV processor to make a strategy change.

A third type of module is the "COMBO" module.
This module combines the functions of the IMS and the EMW modules.