1990 Buick Reatta Coupe
 

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90 Reatta
Can somebody with more knowledge than what I possess suggest the way to proceed to fix this problem? I have a 90 Reatta with 105,000kms. Was working fine, and the day before the event the digital display flickered and all of a sudden said that I have 186,000kms. A few minutes later an error code popped up on the display. Was on the way home, so I disregarded it. The next day I start the car and the whole display is dark/black. Suggestions on what I should do next to repair this?

All you might be able to do would be to verify the instrument panel has good power and grounds.
Other than that you most likely have to sent the unit out for repair.