AUDI A4 1999 B5 / 1.G APB Engine Additional Signals Checking Owner's Manual

24-195
If LED comes on:

Check activation

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

Harness
connector
terminal
VAG1598/31 test box,
socket
1 39

- Repair any open/short circuit as necessary.
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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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24-198

Signal for rough road recognition from
ABS/EDL control module, checking


Note:

The ABS/EDL control module generates the
rough road signal if it recognizes wheel spin on
a wheel. The Engine Control Module (ECM)
switches off the misfire recognition once the
rough road signal is recognized by the ECM.
The rough road signal should only be checked if
the malfunction (P1606) 18014 "Rough Road
Spec Engine Torque ABS-ECU/Electrical
Malfunction" is stored in the DTC memory. It is
possible that the malfunction "Misfiring" is also
stored in DTC memory, however this is then a
sequence error and should be ignored.
The wiring and the rough road signal is
monitored by the ECM.
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24-199

Test conditions

Control module coding OK Page 01
-93
.

Test sequence

- 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 wire from test box socket 74 to ABS
Control Module according to wiring diagram for
short circuit or open circuit.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
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24-200
If no malfunction is detected:

- Replace ABS control module.
If, after the ABS control module has been
replaced the malfunction appears again:

- Replace Engine Control Module (ECM) Page
24
-24
.
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24-201

Data exchange between Engine/ABS/
Transmission control module, checking


Notes:

The data exchange between the various control
modules is carried out via a bus system.
The term "Bus" refers to a system for
transmitting and distributing data.
The wires which connect the control modules
and convey the data between them are called
data wires.
Data is transmitted via data wires in serial, i.e.
in a specific order to the connected control
modules.
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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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