The ABS system on a 1999 Volkswagen Passat is controlled by a separate, standalone computer that is not part of the powertrain control module (PCM). The ABS computer makes decisions about whether or not to engage the ABS system depending upon various factors, such as individual wheel speed and the total speed of the vehicle. When the ABS computer senses a problem with the anti-lock braking system, it will illuminate the ABS malfunction indicator light (MIL). The ABS MIL can only be turned off with an appropriate computerized scan tool and will re-illuminate if the causative problem has not been remedied.
Rotate the ignition to the “ON” position. Do not start the engine.
Locate the vehicle’s diagnostic port. It is underneath the dashboard, about six inches to the right of the steering column.
Plug the scan tool into the diagnostic port and navigate to the “ABS" menu. Select “read codes” and write down the trouble code that is displayed on the scan tool. Save this information for diagnostic purposes.
Select “clear all codes” and watch the dashboard to see if the ABS MIL turns off. Start the engine to verify that the ABS MIL stays off.
Repair the original problem that caused the light to turn on. Repeat Steps 1 through 4 to clear the light again, once the repair is completed.
