display AUDI A4 1995 B5 / 1.G APB Engine Additional Signals Checking Workshop Manual

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Additional signals, checking

Engine speed (RPM) signal, checking


Note:
The engine speed signal is taken from terminal
37 on the Engine Control Module (ECM). The
signal is used for various functions including the
RPM display in the instrument cluster.

Electrical Wiring Diagrams, Troubleshooting & Component Locations - Connect VAG1598/31 test box to wiring harness for engine control
module. Do not connect to the engine control module itself Page 24
-
20
.
- Check wiring from test box socket 37 to instrument cluster according to
wiring diagram for an open circuit.
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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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- Take vehicle for a test drive and check whether
vehicle speed appears in display field 3.

- If vehicle speed does not appear, raise the
vehicle (preferably using a lift) until front left
wheel is clear of the ground.

Electrical Wiring Diagrams, Troubleshooting & Component Locations - Connect VAG1598/31 test box to wiring harness for engine control
module. Do not connect to the engine control module itself Page 24
-
20
.
- Connect diode test lamp between socket 3 (B+) and socket 54 (vehicle
speed signal).
- Switch ignition on and turn front left wheel by hand.
The diode test lamp should flash (very brief flashes).
- If diode test lamp does not flash, check for open circuit or short to B+
or Ground (GND) in wiring between instrument panel and terminal 54
on engine control module connector.
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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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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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If display does not appear as described:

Check switch

- Remove storage compartment on driver's
side.

Repair Manual, Body Interior, Repair Group
68


- Disconnect harness connector on brake
light/brake pedal switch.

- Connect hand-held multimeter for resistance
measurement between terminals 1 and 2.

Note:
The connector slots are marked on the back side
of the connector.
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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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1
2
3
4
- Observe clutch vacuum vent switch switch in display field 2.
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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
X0XX
X1XX

Specified value
X0XX
Clutch pedal not depressed

X1XX
Clutch pedal depressed
Note
Value:
X = insignificant
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If display does not appear as described:

Check switch

- Remove storage compartment on driver's
side.

Repair Manual, Body Interior, Repair Group
68


- Disconnect harness connector on clutch
switch.

- Connect hand-held multimeter for resistance
measurement between terminals 1 and 2.

Note:
The connector slots are marked on the back side
of the connector.


Specified value: approx.: 0

- Depress clutch pedal.


Specified value: (no continuity)
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