There are pages and pages of things that can cause a check engine light. You need to have it checked with a scantool. Then the code can be diagnosed and repaired.
How to change brake lines on a 1991 Buick Lesabre?
the antiloc brake modual is located on the lower left side of the engine compartment up by the radiator but on the fender
Dot 3
Small pedal on the left of the brake pedal - activates the rear brake to hold vehicle
Cut the wire
press back down on the pedal
carb cleaner or brake parts cleaner
Should have an access panel inside trunk
5/16" allen
33 Ft lbs
You may have a vacuum leak at the brake booster. Have the brake booster inspected.
Book time for replacing brake booster 2.6 hrs