Safety Measures and Troubleshooting Basics
ESP is a vehicle safety system. The technician must understand the system completely before working on the system.
CAUTION:
^ The ESP system is basically maintenance free.
^ Repairs should only be carried out by properly trained technicians.
^ If this information is not observed it could lead to damage to the system and a degradation of driving safety.
^ If the On Board Diagnostic (OBD) has recognized a malfunction in the system, the ABS warning light -K47-, the symbol for "Brake system malfunction" and the traction control indicator light -K86- are lit when the ignition is switched on. The red symbol for "Brake system malfunction" appears in the display of the driver information system. The ABS/EDL and ASR/ESP indicator lamps are located below the display. For additional information, Refer to "Indicator lamp functions, overview".
^ If the ABS warning light -K47- and the red symbol for "Brake system malfunction" are not lit, but the brake system is not functioning properly, check for malfunctions in the mechanical/hydraulic brake system components.
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
- First switch the ignition on, and note whether the indicator lamps light up. The table in "Indicator lamp functions, overview") will provide a starting point.
- Observe test conditions.
- Connect the VAG1551 scan tool and select the address word 03 "Brake Electronics".
- Check the control module version and press (arrow) button.
- Check DTC memory . If a DTC is stored: make a note of the DTC and erase the DTC memory.
- End data transfer using the "End Output" function.
- Repair the malfunction with the help of the DTC table. Select again the address word 03 "Brake Electronics." Check and erase DTC memory.
- End data transfer using the "End Output" function. Disconnect VAG 1551 scan tool.
- Make sure all connections are connected properly. Carry out a test drive. The indicator lamps must not light up during the drive. If the indicator lamps 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.
Switch ignition off before carrying out any work on vehicle. Determine anti-theft radio code for radios with anti-theft radio code and disconnect battery Ground (GND) strap.
- Remember that there are certain procedures that must be carried out after connecting the battery, such as: setting the clock. Read procedures under "Reconnecting battery, procedures".
- Only replace a malfunctioning component if you are certain that all electrical lines to this components are functioning properly. The lines must work properly and be capable of carrying all signals without any problems. Check the lines for the following:
^ Corrosion or loose connections in the connectors or Ground straps. If there are bent, broken or corroded contacts on the connectors, replace the contacts using VAS1978 wiring harness repair kit.
^ Open circuit in wiring
^ Short circuit to B+ or Ground (GND)
Refer to Electrical Wiring Diagrams.
Note: The instructions for the VAS1978 wiring harness repair kit generally forbids the repair of any lines in the ESP or related systems. This rule only pertains to the shielded lines in these systems.
- When replacing a control module, make sure you install the correct control module. First check the control module version. The version is displayed after the communication is established between the VAG1551 scan tool and the control module, in the VAG1551 display, or after selecting the "Check Control Module Versions" function 01. You can also determine which equipment is installed in the vehicle using the letter combinations on the vehicle data label.
^ 1AC: Anti-lock Brake System (ABS)
^ 1AH: Anti-lock Brake System with Electronic Differential Lock (ABS/EDL)
^ 1AJ: Anti-lock Brake System with Electronic Differential Lock and traction control system (ABS/EDL/ASR)
^ 1AT: Anti-lock Brake System with Electronic Differential Lock and traction control system (ABS/EDL/ASR) and Electronic Stabilization Program (ESP)
^ All work on the hydraulic unit must be carried out with the utmost cleanliness. Thoroughly clean the hydraulic line connections and the area around them. Do not use any aggressive cleaning agents, such as brake fluid, gasoline, thinning agents, or any fluids containing mineral oil, such as oils and greases. Do not disconnect hydraulic lines until you have cleaned the connections.
^ Note the appropriate precautions regarding handling of brake fluid.
^ Place removed parts on clean surface and cover them. Only use lint-free cloths.
^ Only use genuine packaged parts, and only remove replacement parts from their packaging immediately prior to installation.
^ Bleed brake system if connections in system have been opened.
^ Welding using electrical welding equipment can affect the ESP system.
Test conditions
^ Vehicle equipped with approved wheel and tire sizes, which must be the same on all four wheels. All tire inflation pressures checked according to specification.
^ Mechanical and hydraulic parts of brake system in good condition; no leaks in hydraulic lines and connections (visually inspect ABS hydraulic unit, brake calipers, tandem master brake cylinder).
^ Wheel bearings and wheel bearing play OK
^ Wheel speed sensors installed correctly
^ Supply voltage must be OK (not less than 10.0 volts).
^ Parking brake released
^ Harness connector on ABS control module J104. properly connected, with retainer catch engaged.
^ The OBD sequence can only be started with the vehicle stationary and the ignition switched on (or with the engine running). The diagnosis cannot be started if wheel speed exceeds 2.75 km/h (1.75 MPH), and will be terminated if the speed exceeds 20 km/h (13 MPH).
^ While testing the ESP system, make sure that the vehicle's electrical system is not subjected to electromagnetic interference; keep the vehicle away from equipment with a high current draw such as electric welding units.