You may have to test the actual connections from the switch to the ABS module. I found the connector on the ABS module a little trickier than other connectors is the A3 8V as it has slots longer than usual for the contact terminals to be inserted. I remember having to use a metal pin to help me to insert the terminals so I could place them deep enough in the slots, so I guess you may have a faulty connection if they weren't correctly placed.
I suggest you disconnect the ABS connector (don't forget to disconnect the battery first) and try to check if the wire from the switch is placed in the right slot slot and the terminal is correctly inserted. You might also try to test the electrical connection to the switch but in this case you would have to release the center console trim cover in order to gain access to the switch connector.
I suggest you disconnect the ABS connector (don't forget to disconnect the battery first) and try to check if the wire from the switch is placed in the right slot slot and the terminal is correctly inserted. You might also try to test the electrical connection to the switch but in this case you would have to release the center console trim cover in order to gain access to the switch connector.