To add to GB 's post
This Diagnostic Module trips the CE lamp when it detects an Emmissions Related Fault and stores that code/codes.
You can access CE code/codes from the Black Box in front of the battery . Lift the lid .
You can get this code by pressing the button switch for 2-3 seconds . The code will then flash back a number of times at the LED next to the switch. [ you can check archives for in depth procecdures].
Post your findings and someone will tell you what the code indicates.
You can also erase detcted codes with the same built-in Led/Sw.
Your car has the last of this owner access system...it was eliminated the next year model with the OBDII systems.
[ requiring a scanner]