1995 AUDI A4 airbag

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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always be fastened to and operated from the rear seat by a
second technician. When driving or riding in an airbag equipped vehicle, NEVER hold
the scan tool or other test equipment in your hands or lap while in
motion. Objects between you and and the airbag increase the risk
of injury in an accident.
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24-196

Crash signal, checking

The Engine Control Module (ECM) receives the
crash signal ("Crash shut-down activated") from
the airbag control module.
If the airbag control module sends the crash
signal to the ECM (if an accident occurred or if a
output Diagnostic Test Mode (DTM) was carried
out), the ECM shuts off the fuel pump, that
means the engine stalls, however, afterwards the
engine can be started again (e.g. when removing
the vehicle from the accident area)
The ECM cannot switch off the fuel pump during
an accident if the malfunction "Crash Signal from
Airbag Control Unit/Range Performance" from
the airbag control module is sent to ECM. The
engine control module cannot recognize the
crash signal from the airbag control module; e.g.:
if the wiring between the ECM and the airbag
control module is faulty.

- Connect VAG1598/31 test box to wiring harness
for engine control module. Do not connect to the
engine control module itself Page 24
-20
.
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24-197
Test the following wiring connections for open
circuit and/or short to B+ or Ground (GND) and
open circuit.

VAG1598/31 test
box, socket
Airbag control module,
contact
67 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations
Resistance in wiring: max. 1.5 ohm
Eliminate open circuit or short circuit.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations If no malfunctions are found in wiring: Check
DTC memory of airbag control module.
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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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