AUDI A8 1997 D2 / 1.G ATQ Engine Motronic On Board Diagnostic Workshop Manual

01-1


Motronic, On Board
Diagnostic (OBD)

On Board Diagnostic (OBD), technical
data


Equipment

Data is transmitted between the control module
and the VAS5051 tester or VAG1551 Scan Tool
(ST) via operating mode "Rapid Data Transfer".
DTC memory is designed for permanent
memory and is therefore not dependent on
voltage supply.
Display of stored DTCs occurs after initiation of
display mode Page 01
-15
.

DTC memory must be erased after malfunction
is repaired Page 01
-15
.

Important:

Readiness code must be re-generated after
every time DTC memory is erased Page 01
-
82
.
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01-2

If the ECM recognizes malfunctions that lead to
a degradation of emissions values, it indicates
them by lighting the Malfunction Indicator Lamp
(exhaust warning lamp -K83-). Clarification of
this lamp Page 01
-3 .

"E-Gas"-relevant malfunctions are also
indicated in the instrument cluster by the
warning lamp for Electronic Power Control
("EPC warning lamp").
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01-3

Malfunction Indicator Lamp (MIL),
significance

If the ECM recognizes malfunctions that lead to a
degradation of emissions values, it indicates
them by lighting the Malfunction Indicator Lamp
for exhaust.

Installation position of exhaust MIL
Note:
The Malfunction Indicator Lamp (MIL) can blink or remain lit continuously.
DTC memory should be checked in both cases Page 01
-15
.
Blinking: There is a malfunction that causes damage to the catalytic
converter in this driving condition (e.g. combustion misfire). In this
case, vehicle must only be driven at reduced power! Continuously lit: There is a malfunction that causes increased
emissions. Check DTC memory for Motronic ECM and automatic
transmission (if installed). If there are driveability problems or if there is a customer complaint
and the exhaust MIL is not lit, DTC memory must be checked. There
may be DTCs stored that do not cause the exhaust MIL to light up
immediately, but only if malfunction is recognized again after repeated
engine starts.
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01-4

Malfunction Indicator Lamp (MIL),
checking


Special Tools and Equipment

VAG1594A

VAG1598/31
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01-5

Function test of warning lamp

- Switch ignition on.


Warning lamp for On Board Diagnostic
(Malfunction Indicator Lamp -MIL-) must
light up

A - Warning lamp for On Board Diagnostic
(Malfunction Indicator Lamp -MIL-) does not
light up

- Connect VAG1598/31 test box at wiring harness
to ECM, do not connect ECM Page 24
-17
.

- Bridge sockets 1 and 47 of test box.

- Switch ignition on.


Warning lamp must light up.
If warning lamp does not light up:

- Switch ignition off.

- Remove instrument cluster:

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Repair Manual, Electrical Equipment, Repair
Group 90, Instrument cluster, removing and installing

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01-6

- Check the following wire connection for open
circuit and short circuit to B+:

Test box
VAG1598/31
Socket
Instrument cluster

Terminal
47 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations binder

- Repair open circuit or short circuit if
necessary.
If wire connection is OK:

- Replace Engine Control Module (ECM) Page
24
-21
.
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01-7

B - Warning lamp for On Board Diagnostic
(Malfunction Indicator Lamp -MIL-) remains lit
constantly

- Check DTC memory of Engine Control Module
(ECM) Page 01
-15
.
If no DTCs are stored:

- Connect VAG1598/31 test box at wiring harness
to ECM, do not connect ECM Page 24
-17
.

- Remove instrument cluster:

Repair Manual, Electrical Equipment, Repair
Group 90, Instrument cluster, removing and installing


- Check the following wire connection for short
circuit to Ground (GND):

Test box
VAG1598/31
Socket
Instrument cluster

Terminal
47 Electrical Wiring Diagrams,
Pa
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Troubleshooting & Component
Locations binder

- Repair short circuit if necessary.
If wire connection is OK:

- Replace Engine Control Module (ECM) Page
24
-21
.
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01-8

Safety precautions

If special testing equipment is required during
road test, note the following:

WARNING!

Scan tools and testing devices must always
be secured on the rear seat and operated
from there by a second person.
If a scan tool or testing device were to be
operated from the passenger seat and there
were an accident involving activation of the
passenger-side airbag, the person seated
there could be seriously injured.
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