Sorry, was away. My 2001 has the older 22 pin DLC (Diagnostic Link Connector) inside the engine bay on the RHD Drivers side. There is a fairly simple manual procedure to test the ABS using this connector. Mine does not have the newer DLC which is OBD2 compliant which is found in the 100 series from 2003 (?? depends where its from apparently). The manual procedure involves removing a crossover bus and then shorting two pins, which leads to a two part sequence of flashing lights on the dash which you use to form a two digit number which you then look up in the FSM/online.
Having said all that it's probably one of your rear speed sensors.
The older pre OBD standard codes on mine can be read using a scan tool with an adapter cable. The scan tool I think is called mini-vci and the custom software is called Techstream which they send you (Ebay / Aliexpress - bootlegged ?) with the tool.