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HOMESERVICE MANUALSAUDI1999A8 QUATTROREPAIR AND DIAGNOSIS (SINGLE PAGE)BRAKESANTI-LOCK BRAKESON BOARD DIAGNOSTIC (OBD) - ABS/EDL/ASRELECTRONIC STABILIZATION PROGRAM (ESP)SAFETY MEASURES AND TROUBLESHOOTING BASICSTEST DRIVE
1999 Audi A8 Quattro

Test drive

1999 Audi A8 QuattroSECTION Test drive
  • Some DTCs are only recognized by the On Board Diagnostic while the vehicle is moving. You can check the system by carrying out a test drive. During the test drive, drive at 60 km/h for 30 seconds. Make sure the traffic is clear and then brake hard enough to activate the ABS. You will feel a pulsing in the brake pedal indicating the system is active.
CAUTION: If the OBD has recognized a malfunction then the brake system is only partially functional. Because the brake pressure at the rear wheels is no longer regulated via Electronic Brake Distribution (EBD), the rear wheels can lock even during light braking. This can cause the rear end of the vehicle to break loose and therefore lead to an accident.

If the customer has reported a malfunction or problem, troubleshoot according to the customer complaint 

CAUTION: If test and measuring instruments are required during a test drive, these must always be secured to the rear seat and operated by a second person from this position. If test equipment were operated from the front passenger seat, the person sitting there could be injured if the front passenger airbag were triggered in the event of an accident.
  • First switch the ignition on, and note whether the indicator lights light up. The table in INDICATOR LIGHT FUNCTIONS, OVERVIEW  will provide a starting point.
  • Observe test conditions. See TEST CONDITIONS  .
  • Connect the VAG1551 scan tool and select the address word 03 "Brake Electronics". See VAG1551 SCAN TOOL (ST), CONNECTING AND ENTERING ADDRESS WORD  .
  • Check the control module version (see CONTROL MODULE VERSIONS (SCAN TOOL FUNCTION 01), CHECKING  ) and press --> button.
  • Check DTC memory. See DIAGNOSTIC TROUBLE CODE (DTC) MEMORY (SCAN TOOL FUNCTION 02), CHECKING  . If a DTC is stored: make a note of the DTC and erase the DTC memory. See ERASE DTC MEMORY  .
  • End data transfer using the "End Output" function. See END OUTPUT  .
  • Repair the malfunction with the help of the DTC table. See DTC TABLE; DTCS 00000 TO 00526  . Select again the address word 03 "Brake Electronics." Check and erase DTC memory.
  • End data transfer using the "End Output" function. Disconnect VAG1551 scan tool.
  • Make sure all connections are connected properly. Carry out a test drive. See TEST DRIVE  . The indicator lights must not light up during the drive. If the indicator lights light up during the test drive, repeat the troubleshooting procedure.
    NOTE: If the control module connector is disconnected during the drive, an unfounded DTC may be stored in the memory of another control module. The mechanical and hydraulic brake system functions will continue to work. However, with a system failure the brake pressure regulator is deactivated meaning there is an increased chance of an accident while driving.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.