1998 VOLKSWAGEN JETTA Service Manual

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Safety precautions
Observe following if test and measuring
instruments are required during a test drive:

Test and measuring instruments must be
secured to rear seat and operated by a 2nd
person from this location.

When test and measuring instruments are
operated from the front passenger seat there is
a danger that the person sitting there could be
injured in an accident when the airbag is
triggered.
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- Connect V.A.G 1551 Scan Tool and select
address word 03 for"Brake electronics" with
ignition switched on; Page 01
-23
Rapid data transfer HELP
Select function XX Indicated on display
- Press keys 0 and 8 to select function "Read
measured value block".
Rapid data transfer Q
08 - Read measured value block Indicated on display
- Confirm entry with key Q.
Read measured value block
Enter dis
play group number XXX
Indicated on display
- Enter display group number List of selectable
display group numbers, Page 01
-64 .
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List of selectable display group numbers
Display group number
Display zone
Designation
001 1 Wheel speed at left front wheel sensor (km/h)
2 Wheel speed at right front wheel sensor (km/h)
3 Wheel speed at left rear speed sensor (km/h)
4 Wheel speed at right rear speed sensor (km/h)
002 1 Wheel speed at left front speed sensor (km/h)
2 Wheel speed at right front wheel sensor (km/h)
3 Wheel speed at left rear speed sensor (km/h)
4 Wheel speed at right rear speed sensor (km/h)
003 1 Brake light switch
2 Vacant
3 Vacant
4 Vacant
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Display group number
Display zone
Designation
006 1
Longitudinal acceleration sensor -G251-
1)
2 Vacant
3 Vacant
4 Vacant
125 1 Data bus for engine
2
Data bus for four-wheel drive
1)
3
Data bus for transmission
2)
4 Vacant
1) Four-wheel drive vehicles with Haldex coupling only.
2) Vehicles with automatic transmission only.
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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.
Read measured value block
1
1 2 3 4
There are always 4 display zones -arrows-
in the measured value block. Decoding the
individual values in display zones 1 to 4 can
be read from the following tables.
Read measured value block 1
0 km/h 0 km/h 0 km/h 0 km/h
Indicated on display: (vehicle stationary)
Press C key for the next display group
number entry.
If the key is pressed, keys 0 and 8 for
work sequence "Read measured value
block" must be pressed again afterwards to
regain entry.
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Note:
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).
Read measured value block
1 Display group number: 001
0 km/h 4 km/h 0 km/h 0 km/h
Indicated on display: (Example)

Wheel speed at right rear speed sensor
(0 to 255 km/h)

Wheel speed at left rear speed sensor

(0 to 255 km/h)

Wheel speed at right front speed sensor
(0 to 255 km/h)

Wheel speed at left front speed sensor

(0 to 255 km/h)
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Checking speed sensor

Display group number 002

- Press keys 0, 0 and 2.

- Confirm entry with key Q.
Read measured value block
2
1 2 3 4
There are always 4 display zones -arrows-
in the measured value block. Decoding the
individual values in display zones 1 to 4 can
be read from the following tables.
Read measured value block 2
255 km/h 255 km/h 255 km/h 255 km/h
Indicated on display: (Vehicle stationary)
Press C key for the next display group
number entry.
If the key is pressed, keys 0 and 8 for
work sequence "Read measured value
block" must be pressed again afterwards to
regain entry.
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Note:
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 ABS Control Module (w/EDL) -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.
Read measured value block
2 Display group number: 002
3 km/h
1)
6 km/h1)
2 km/h2)
1 km/h2)
Indicated on display: (when driving off slowly)

Wheel speed at right rear speed sensor
(0 to 255 km/h)

Wheel speed at left rear speed sensor

(0 to 255 km/h)

Wheel speed at right front speed sensor
(0 to 255 km/h)

Wheel speed at left front speed sensor

(0 to 255 km/h)
1) If the deviations in display zones 1 and 2 are greater than 6 km/h (approx. 3.75 mph), the
following malfunctions may be present:
2) If the deviations in display zones 3 and 4 are greater than 2 km/h (approx. 1.25 mph), the
following malfunctions may be present:
Note:

Air gap between speed sensor and rotor may be too wide.
- Check that speed sensor is attached correctly to wheel bearing housing.

Speed sensor or rotor exterior damaged.
- Change damaged component.
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