I don't think it is as easy to get the fault code from a 1990 car? because they used a different system for this year. The system was changed in 1991 and the diagnostic port was added to the connector under the rear seat. The connector is only 2-pin's and you follow the instructions to retrieve the fault code. Use a paper-clip or similar to jump the connector - this will allow you to read the fault code from a series of flashes of the ABS warning lamp. If you can't find the full instructions just let me know and I will post them.