On Board Diagnostic (OBD)

On Board Diagnostic (OBD), performing

Test prerequisites for OBD
- The tires installed to all wheels must be of the same (approved) size; tires inflated to prescribed pressure.
- Mechanical/hydraulic parts of the brake system including brake light switch and brake lights OK.
- Hydraulic lines and connections not leaking (visual check of hydraulic unit, brake calipers, wheel cylinders, tandem master brake cylinder).
- ABS Control Module (w/EDL) -J104- is correctly bolted to ABS Hydraulic Unit -N55-.
- Connector on ABS Control Module (w/EDL) -J104- correctly plugged-in (retainer is engaged).
- Check contacts of ABS components for damage and correct seating.
- All fuses according to wiring diagram OK (remove fuse from fuse holder to check).
- Supply voltage OK (at least 10.0 V).
- Access to the OBD is only possible when the vehicle is stationary and ignition turned on (or engine running).
- Wheel bearings and wheel bearing play are OK.
- When checking the ABS system make sure that the vehicle electric system is not affected by electro-magnetic interference, i.e. the vehicle is kept away from equipment with a high current draw, e.g. from an electric welding module.

Safety precautions

WARNING:
- You must always secure testing and measuring equipment on the rear seat.
- When vehicle is being driven, a second technician must operate this equipment.

Scan tool, connecting
All functions which could previously be performed with V.A.G 1551/1552 can also be performed with the new tester VAS 5051 in the operating mode vehicle OBD.

Special tools and equipment





- VAS 5051 Vehicle Diagnosis, Testing and Information System
- Diagnostic cable VAS 5051/1 or VAS 5051/3
- The ABS function is switched off in the control module during the On Board Diagnostic (OBD).
- The Diagnostic Trouble Code (DTC) memory can be erased after successfully checking and repair.

Connecting VAS 5051





- Pull cover -1- off in direction of arrow.
- With ignition switched off, connect tester VAS 5051 to Data Link Connector using diagnosis cable VAS 5051/1 or VAS 5051/3.

Selecting operating mode:
- Press button on display for "Vehicle On Board Diagnostic (OBD)".

Selecting vehicle system:
- Press button "03 brake electronics" on the display.
The control module identification and coding are indicated on the display.

Selecting diagnosis function:
All diagnostic functions available are indicated on the display.
- Press button on display for desired function.
- Further measures see repair procedures.

Note: The following test sequences are for V.A.G 1551 scan tool.