display AUDI A4 1996 B5 / 1.G AWM Engine Additional Signals Checking Workshop Manual

24-164

Engine speed signal, checking


Note:
The engine speed signal is output at terminal 37
of the Engine Control Module (ECM). The signal
is used, among other things, for RPM display in
the instrument cluster.

- Connect VAG1598/31 test box at wiring harness
to Engine Control Module (ECM), do not connect
ECM Page 24
-19
.

- Check the following wire connection for open
circuit and short circuit to Ground (GND) and B+:

Test box
VAG1598/31
Socket
Instrument cluster

Terminal
37 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations

- Repair open circuit or short circuit if
necessary.
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Vehicle speed signal, checking


Notes:

The vehicle speed signal is generated by the
speedometer Vehicle Speed Sensor (VSS) -
G22- (at transmission) and is processed in the
instrument cluster.
The processed signal enters at terminal 54 of
the ECM and is used for idle stabilization and
tip-in shock reduction during shifting.

Test requirement:
Function and display of speedometer OK.
Troubleshooting:

Repair Manual, Electrical Equipment, Repair
Group 90; Instrument cluster; Speed signal, checking


Test sequence

WARNING!

To reduce the risk of accident during road
tests, always observe safety precautions
Page 24
-1 .
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Display on VAS5051:
- Select diagnostic function "08 - Read Measuring Value Block" in
selection -1-.

Display on VAS5051:
1 - Enter display group Max. input value = 255
- Select function "005" in button field -2- for "display group number 005"
and press Q button to confirm input.
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Display on VAS5051:
- Determining via road test whether vehicle speed is displayed in display
field -3-.
- If vehicle speed is not display, lift vehicle -if possible using a vehicle lift-
until front left wheel is free.
- Connect VAG1598/31 test box at wiring harness to Engine Control
Module (ECM), do not connect ECM Page 24
-19
.
- Connect VAG1527B voltage tester to sockets 3 (B+) and 54 (VSS) of
VAG1598/31 test box.
- Switch ignition on and turn front left wheel by hand.

LED must blink (very brief blink signal).
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24-170

Test requirements:

A/C system OK
No DTCs in DTC memory of Engine Control
Module (ECM).
Vehicle at room temperature (warmer than
+15 C).

Test sequence

- Connect VAS5051 tester Page 01
-7 and
select vehicle system "01 - Engine electronics".
Engine must run at idle for this.

Display on VAS5051:
- Select diagnostic function "08 - Read Measuring Value Block" in
selection -1-.
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Display on VAS5051:
1 - Enter display group Max. input value = 255
- Select function "050" in button field -2- for "display group number 050"
and press Q button to confirm input.

Display on VAS5051:
- Switch A/C system off.

Specified value in display field -4-: Compr. OFF
- Switch A/C system on using "Auto" button and adjust A/C system to
maximum cooling or heating power. Compressor must run.
Specified value in display field -4-: Compr. ON
- Depress gas pedal completely (swiftly) and then release it (brief
acceleration).
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Display on VAS5051:
If indications do not resemble description:
Repair Manual, Heating & Air Conditioning, Repair Group 01; On Board Diagnostic (OBD) of A/C system

Specified value in display field -4-: Indication jumps for a few
seconds from "Compr. ON" to "Compr. OFF" (compressor is
switched off when vehicle accelerates).
- Connect VAG1598/31 test box at wiring harness to Engine Control
Module (ECM), do not connect ECM Page 24
-19
.
- Check the following wire connection for open circuit and short circuit to
Ground (GND) and B+:
Test box
VAG1598/31
Socket
A/C control
head -E87-
Terminal
41 Electrical Wiring Diagrams, Troubleshooting &
Component Locations
- Repair open circuit or short circuit if necessary.
- If there are no malfunctions in the wiring, check function of A/C system.
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Display on VAS5051:
- Select diagnostic function "08 - Read Measuring Value Block" in
selection -1-.

Display on VAS5051:
Note:
Measuring value blocks 125 and 126 indicate the participants in the
powertrain data-BUS. 1 - Enter display group Max. input value = 255
- Select function "125" in button field -2- for "display group number 125"
and press Q button to confirm input.
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Display on VAS5051:
- Check indications in display fields -1- through -4-.
CAN capable control modules connected to the Engine Control Module
(ECM) are indicated:

No indication: 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
-
Press button to change into display group 126.
- Check under display group 126 in the same manner.
-
Press "08 - erase DTC memory" to end function -button.

Display on VAS5051:
- Select diagnostic function "06 - end output" in selection -1-.
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Display on VAS5051:
When a control module responds with its identification, the display
indicates the number of stored errors or indicates "no malfunctions
recognized".
DTCs stored in the system are indicated in sequence and printed out.
Then the VAG1551 scan tool sends the next address word.
If a malfunction related to the"powertrain databus" or the "CAN-bus" is
indicated:
If the correct control modules are installed: - In selection -1-, press diagnostic function "00 - Check DTC memory -
complete system".

DTC memory of all OBD capable systems in the vehicle will be
checked.
- Check whether the Engine Control Module (ECM) and other CAN
capable control modules installed are appropriate for this vehicle (part
no. and coding).
- Check to be sure the multi-pin connectors of the control modules are
securely connected.
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