Volkswagen Workshop Service and Repair Manuals

• ◆ All functions that have so far been carried out with V.A.G 1551 can now also be carried out with the tester VAS 5051.

The control unit can transfer a considerable amount of test data. This test data delivers information on the operational condition of the system and/or sensors connected to it. In many cases the transferred test data supports fault finding and fault rectification. The test data has been summarized into single display groups because all the information cannot be evaluated at the same time. The information can be selected via display group numbers.

Safety measures

• ‒ Connect fault reader V.A.G 1551 and select brake electronics control unit with ignition switched on (address word 03);

• ‒ Press keys 0 and 8. (The function "Read measured value block" is initiated with 08.)

• ‒ Confirm entry with key Q.

• ‒ Enter display group number => List of selectable display group numbers, Page 01-53 .

List of selectable display group numbers

Test sequence and test tables with measured values

Checking speed sensor allocation

Display group number 001

• ‒ Press keys 0, 0 and 1
• ‒ Confirm entry with key Q.

Press C key for the next display group number entry.

If the ⇒key is pressed it must be continued with keys 0 and 8 for work sequence "Read measured value block".

For display group number 001 remember:

The actual wheel speeds are displayed. They serve to check the speed sensor allocation to the wheel. (The vehicle must be raised and the wheel must be rotated by hand by a 2nd mechanic).

Checking speed sensor

Display group number 002

• ‒ Press keys 0, 0 and 2
• ‒ Confirm entry with key Q.

Press C key for the next display group number entry.

If the ⇒key is pressed it must be continued with keys 0 and 8 for work sequence "Read measured value block".

For display group number 002 remember:

The reading of measured value blocks in display group number 002 must be undertaken when driving off slowly. Then the control unit -J104- will store the first usable voltage signals provided by the speed sensors and display these as a fixed value in the measured value block.

1)     If the deviations in display zones 1 to 4 are greater than 6 km/h (approx. 3.75 mph), the following faults may be present:

• ◆ Air gap between speed sensor and rotor may be too big.

- Check that speed sensor is screwed correctly to wheel bearing housing.

• ◆ Speed sensor or rotor exterior damaged.

- Change damaged component.

Checking brake light switch for ABS function

Display group number 003

• ‒ Press keys 0, 0 and 3
• ‒ Confirm entry with key Q.

Press C key for the next display group number entry.

If the ⇒key is pressed it must be continued with keys 0 and 8 for work sequence "Read measured value block".