ESP AUDI A4 1998 B5 / 1.G Brakes OBD Workshop Manual

01-1


On Board Diagnostic (OBD)

On Board Diagnostic (OBD), basic
information

The control module of a system with OBD
detects malfunctions during vehicle operation
and stores them as Diagnostic Trouble Codes
(DTCs) in a permanent memory. The DTCs
remain intact in the memory if the power supply
from the battery is interrupted.
The OBD function relates to the electrical and
electronic parts of a system; in other words it
only registers malfunctions which have an effect
on the electric signals.
On Board Diagnostic (OBD) helps technicians
perform a more targeted diagnostic
troubleshooting. Use the VAG1551/1552 Scan
Tools (ST) or the VAS5051 tester to achieve the
potential offered by On Board Diagnostic (OBD).
To do this, the scan tool and the respective
control module must exchange data. They must
communicate with each other.
The Data Link Connector (DLC) is the interface
for communication between the control module
and the scan tool.
Troubleshooting is started by connecting the
scan tool to the Data Link Connector (DLC). This
establishes a data link between the control
Pa
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gnostic
(OBD
)
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01-8

Note:
For example: Pressing buttons -0- and -3-
selects the "Brake Electronics" address word 03. Rapid data transfer
Q
03 Brake electronics

Indicated on display:
Rapid data transferScan tool sends address word 03 - Press -Q- button to confirm input.
Indicated on display after entering address word 03:
Note:
If a malfunction occurs when establishing communication between the
VAG1551 scan tool and the control module, refer to the four displays and
instructions that follow.
Rapid data transfer
HELP
Control module not respondin
g!

Rapid data transfer
HELP
K-wire not switchin
g to Ground / B+

- Press the "HELP" button to print a list of possible causes of the
malfunction.
Rapid data transfer
HELP
No si
gnal from control module

Electrical Wiring Diagrams, Troubleshooting & Component Locations - Test cable connections for data link connector wire -K-.- Test power supply and Ground (GND) connections for ABS control
module (w/EDL) -J104-.
Pa
ge 9 of 12 On Board Dia
gnostic
(OBD
)
11/20/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.SU02.01.1