The ABS computer stores trouble codes just like the engine computer does. The ABS computer on '90-'93 Integras is located inside the passenger side rear seat side panel. It has an LED light on it that blinks out the codes. There is a square access window covered by a plug on that panel that lets you see the LED. It's the smaller of the two plugs in the panel.

I'll upload the pages from the Helms manual to show you how to check the code.