Safety Precautions and General Troubleshooting Information

Safety precautions and general troubleshooting information
Road testing

WARNING:
- If you drive the vehicle after a malfunction has been detected by OBD, bear in mind that the function of the brake system is limited, and there is a risk of accident. The brake pressure at the rear wheels is no longer controlled by the Electronic Brake Distribution (EBD) function. This can result in excessive braking at the rear, and the vehicle may skid unexpectedly under braking.
- When driving or riding in an airbag-equipped vehicle, NEVER hold the scan tool or other test equipment in your hands or lap while in motion. Objects between you and the airbag increase the risk of injury in an accident.
- During a test drive in an airbag-equipped vehicle, test equipment must always be fastened to and operated from the rear seat by a second technician.

Certain malfunctions will only be detected when the car is moving, so a road test is required in order to check the system. Maintain speed above 60 km/h (38 mph) for 30 seconds, then apply the brakes hard enough to activate ABS-controlled braking at least once (pulsation must be felt at the brake pedal).

If there is a malfunction:
- Switch ignition on and observe warning light. The table under Warning lamp functions will give an initial indication of what to look for. Refer to Warning lamp functions.
- Observe test conditions
- Connect VAG1551 scan tool and insert "Brake Electronics" address word 03.
- Check control module version.
- Check DTC memory. Checking DTC Memory (Scan Tools Function 02)

If a DTC is stored in memory, make note of it and then erase DTC memory. Erase DTC Memory
- End data transfer using "End Output" function 06. End Output
- Repair malfunction according to instructions in DTC table.
- Select "Brake Electronics" once again using address word 03.
- Check and erase DTC memory.
- End data transfer using "End Output" function 06 and disconnect VAG1551 scan tool.
- Make sure all harness connectors are properly connected.
- Road test.
Warning lamps should not light up during the road test. If they do, the troubleshooting procedure must be repeated.

Note: If the harness connector is not connected to the control module while the vehicle is moving, a sporadic DTC may be stored in DTC memory for another control module. The mechanical and hydraulic elements of the brake system will still function in the normal way, but the Electronic Brake Distribution (EBD) function is not available when the ABS/EDL system is inactive.

WARNING: If you drive the vehicle after a malfunction has been detected by OBD, bear in mind that the function of the brake system is limited, and there is a risk of accident. The brake pressure at the rear wheels is no longer controlled by the Electronic Brake Distribution (EBD) function. This can result in excessive braking at the rear, and the vehicle may skid unexpectedly under braking.

Test conditions
- Vehicle equipped with approved wheels 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
- ABS wheel speed sensors installed correctly
- Supply voltage must be OK (not less than 10.0 volts)
- 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 (1.5 mph), and will be terminated if the speed exceeds 20 km/h (13 mph).
While testing the ABS/EDL and ABS/EDL/ASR systems, 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.