lock AUDI A4 1998 B5 / 1.G APB Engine Additional Signals Checking Workshop Manual

24-182

Vehicle Speed Signal (VSS), checking


Notes:

The vehicle speed signal is generated by the
Vehicle Speed Sensor (VSS) -G68 (on the
transmission) and is processed in the
instrument cluster.
The processed signal goes to terminal 54 on
the engine control module and is used for Idle
Air Control (IAC) and for the damping of load
change jolts when changing gear.

- Start engine.

- Connect vehicle diagnostic, testing and
information system VAS 5051 or VAG1551 scan
tool and select engine electronics control
module by entering address word "01" Page 01
-9 .

- Select "Read measured value block" (function
08) and Display Group 5. Read Measuring Value Block 5
1
2
3
4

Indicated on display:
Warning!
During a road test in an airbag equipped vehicle, VAG1551 must
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24-185

Brake light switch -F and brake pedal
switch -F47, checking


- Connect vehicle diagnostic, testing and
information system VAS 5051 or VAG1551 scan
tool and select engine electronics control
module by entering address word "01" Page
01
-9 .
When doing this the ignition must be switched
on. Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -8- to select function "Read Measuring Value
Block" and confirm entry with -Q- button.
Read Measurin
g Value Block
Input displa
y group number XXX

Indicated on display
- Press buttons -0-, -6- and -6- to select "display group number 066" and
confirm entry with -Q- button.
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24-186

Read Measuring Value Block 66
1
2
3
4

Indicated on display
- Observe brake light/brake pedal switch in display field 2.

Display fields

1 2 3 4
Display Group 066: Signals to engine control module
Display xxx km/h
X X X X xxx km/h 0 0 0 0
Indicates Actual speed
Switch positions Specified speed Switch positions
Work
range
XX00
XX11

Specified value
XX00
Brake pedal not depressed

XX11
Brake pedal depressed
Note
Value:
X = insignificant
The switch points are offset
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24-191

Clutch Vacuum Vent Valve Switch -F36,
checking


Note:
This signal is used to avoid RPM over-oscillation
and load change impacts when changing gears
and is also used for the cruise control system.

Test sequence

- Connect vehicle diagnostic, testing and
information system VAS 5051 or VAG1551 scan
tool and select engine electronics control
module by entering address word "01" Page
01
-9 .
When doing this the ignition must be switched
on. Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -8- to select function "Read Measuring Value
Block" and confirm entry with -Q- button.
Read Measurin
g Value Block
Input displa
y group number XXX

Indicated on display
- Press buttons -0-, -6- and -6- to select "display group number 066" and
confirm entry with -Q- button.
Read Measuring Value Block 66

Indicated on display
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24-202

Checking bus system
The principle of the test is independent of the
number of control modules/systems connected to
the CAN-bus.
The DTC table suggested checking the data
exchange between the Engine Control Module
(ECM) and CAN capable control modules.

- Start engine (if engine will not start, switch
ignition on).

- Connect VAS5051 tester or VAG1551 scan tool
and select the control module for engine
electronics using "address word" 01 Page 01
-
9 .
Rapid data transfer
HELP
Select function XX

When indicated on display:
- Press buttons -0- and -8- to select "Read Measuring Value Block" and
press -Q- button to confirm input.
Read measurin
g value block
Q
Enter displa
y group number XXX

When indicated on display:
- Press buttons -1-, -2- and -5- to select "display group number 125" and
press -Q- button to confirm input.
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24-203

Read measuring value block 125
1
2
3
4

When indicated on display:
- Check indications in display fields 1 through 4.
CAN capable control modules connected to the Engine Control Module
(ECM) are indicated:

No indication (display field empty): Control module not CAN-
capable
Indication 1: CAN capable control module is connected to databus
Indication 0: CAN capable control module is not connected to
databus (e.g. in case of malfunction)
Read measuring value block 125
ABS 1
Combi 1

Example:
Note:
Display group 125 indicates all systems that communicate with the Engine
Control Module (ECM) via the CAN-bus. (In this example, the ABS control
module and the instrument cluster). If these systems are not installed, the
display fields in display group 125 that are intended for them will be
empty. Display field 1 will indicate "Transmission 1" and display field 4 will
indicate "A/C 1" if these systems are communicated with the Engine
Control Module (ECM) via the CAN-bus.
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24-204

Read measuring value block 126
1
2
3
4

Note:
Display group 126 indicates all other systems that communicate with the
Engine Control Module (ECM) via the CAN-bus. If these systems are not
installed, the display fields that are intended for them will be empty.
The following systems will be indicated in display group 126, assuming
they are communicating with the Engine Control Module (ECM) via the
CAN-bus:
Display field 1: automatic distance control; indication: "Distance 1".
Display field 2: Steering angle sensor; indication: "Steering angle 1"
Display field 3: Airbag; indication: "Airbag 1".
Display field 4: System voltage; indication: "cnt. ELEC 1". - Check under display group 126 in the same manner.
-
Press button.
Rapid data transfer
HELP
Enter address word XX

When indicated on display:
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