The Buick Reatta was an electronically advanced automobile for the time they were built. They had three separate computer systems on board. Additional electronic components were an electronic digital instrument panel, a Cathode Ray Tube (CRT) touch screen panel to control the climate control system and the remotely located radio and cassette player. All this was possible by connecting the various systems together with a serial bus that carried information from one component to another allowing them to "talk" to each other.
The Reatta's Engine Control Module (ECM) is responsible for controlling the engine management system. Using inputs from various sensors, the ECM adjusts the fuel injection to supply the proper fuel/air mixture going into the engine. It also adjusts the ignition spark timing of the engine for optimum engine operation.
The Body Control Module (BCM) takes inputs from various switches, sensors, and your input on the CRT touch screen to determine how to control the Reatta's heat and a/c system to maintain a specified cabin temperature automatically. It uses your input on the CRT touch screen to control the radio, cassette or CD player. It also controls the interior lights based on input from switches inside the doors.
There is an Electronic Brake Control Module (EBCM) mounted in the trunk of your Buick Reatta that processes input signals from sensors mounted on the wheels to determine when a wheel has stopped turning as in a skid. When it detects a skid it will activate the Anti-lock Braking System (ABS) valves that will modulate the braking power going to each wheel to ensure the wheels have the optimum braking power without sliding.
The Ignition system on the Buick Reatta uses an Ignition Control Module (ICM) to trigger the coils to fire the spark plugs. The Crankshaft Position Sensor tells the ECM when the crankshaft is in the proper position for the ICM to fire each spark plug.
When problems with the Buick Reatta's electrical systems arise there is an on-board diagnostic system that can help you pinpoint the cause of the problem. The first indication you will see that you have a problem is a warning message on the instrument panel and/or the CRT screen. The warning messages could be intermittent or constant depending on the conditions that caused the warning message to be displayed. With most messages you can continue to safely drive your car home or to a repair facility.
If you receive a warning message that tells you your car is overheating or has low oil pressure, stop driving and turn the engine off as soon as you can safely get to the side of the road. Continuing to drive the car when these warnings are displayed could cause sever damage to your engine.
The Buick Reatta has an on-board diagnostic system that can assist you with tracking down problems with your Reatta. Information on how to access the diagnostic system can be found here.
Most of the Buick Reatta's electrical components use an isolated ground wire, (sometimes referred to as a dedicated ground wire), that goes back to a ground junction box located behind the battery. This isolated ground wire insures there will be no interference from the engine that could cause problems with the delicate electronic components in the Reatta. As these cars age the isolated ground wires can become loose or corroded. All Buick Reatta owners should clean and tighten the isolated ground wires at the junction box if they have not done so. More information about the location of the isolated ground wires can be found here.
Another area of concern on these older cars is the wire splices under the seats. Especially in cars that are parked out in the weather. If water enters the car it makes it's way to the lowest part of the car, under the seats where a large number of wires are spliced together. Reatta convertibles and coupes with sunroofs are the most susceptible to having problems with the splices although it can happen to any Reatta exposed to the elements. If you are having problems with interior lights not working, side mirrors not working, or other unexplained electrical malfunctions the wire splices under the seats could be the cause of your problems. Read more about wire splices under the seats.