"Anti-Lock" Light
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 1989 Audi 90, 1989 Audi 80, 1989 Audi 200, 1989 Audi 100, and 1988 Audi 90. However, it is still accessible from the selected car via links, so may be relevant.
If the anti-lock indicator light comes on while driving but the ABS system is still operating (evident by pulsating brake pedal during hard stops), check voltage supply at "D+" terminal on alternator and at terminal No. 15 of ABS control unit. All test values quoted refer to digital multimeter and ABS tester.