1998 AUDI A4 ECO

01-2

The Exhaust Malfunction Indicator Light (MIL) in
the instrument cluster will be switched on if the
engine control module recognizes malfunctions
which have an affect (decrease emissions) on
exhaust emissions Page 01
-3 .

Malfunctions relating to the electronic throttle
are also indicated by a Electronic Power
Control (EPC) warning light in the instrument
cluster.
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01-3

Exhaust Malfunction Indicator Light
(MIL), significance

If the Engine Control Module (ECM) recognizes
emission related malfunctions, this is indicates by
the MIL coming on.

Component location of MIL
Note:
When a recognized malfunction switches on the MIL, it will either blink or
light continuously. In either case, the DTC memory must be checked
Page 01
-15
.
If the MIL starts to blink, there is a malfunction that can lead to damage of
the Three Way Catalytic Converter (TWC). In this case driving should be
only continue with reduced power until the MIL goes out or stays on
continuously.
Continuos MIL
If the MIL lights continuously, there is malfunction that affects exhaust
emissions. In this case the DTC memory of the ECM and Transmission
Control Module (TCM) (if equipped) must be checked.
Some malfunctions may occur without causing the MIL to come on. When
driveability or performance problems are reported and there is no
indication from the MIL, the operation of the MIL must be checked. In
addition, the DTC memory of the ECM and TCM must be checked, as
there may be malfunctions stored that do not switch the MIL on
immediately.
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01-5
If MIL remains lit for more than 3 seconds (i.e.
continuously) when ignition is on, proceed with
test as follows:

- Start engine and allow it to run at idling speed.

Specification: MIL should go out.
If the MIL does not go out:

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

Cause:
MIL is activated
via short circuit
to Ground
(GND). Corrective action:
If the specification is not - Switch ignition off
- Connect VAG1598/31 test
box . Do not connect engine
control module.
- Measure resistance between
vehicle Ground and socket 47
on test box. Specification:
infinity (because the wire
should not have any direct
Ground connection)
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01-7

Mode under Address word 33:
Mode 1: Transmit diagnostic data Switch ignition on or let engine run at idle
Mode 2: Transmit operating conditions Switch ignition on or let engine run at idle
Mode 3: Check DTC Memory Switch ignition on or let engine run at idle
Mode 4: Erase diagnostic data Switch ignition on or let engine run at idle
Mode 5: Output of oxygen sensor signals Switch ignition on or let engine run at idle
Mode 6: Transmit measured values Switch ignition on or let engine run at idle
Mode 7: Check DTC Memory Switch ignition on or let engine run at idle
Mode 8: Check tank leak test Switch ignition on or let engine run at idle
Mode 9: Read out vehicle information Let engine run at idle Mode 1 to 9 can be selected under address word 33.

Individual measured values can be read out under mode 1. Mode 1 is not recommended for authorized Audi service
centers, since the data can be obtained much more accurately under address word 01 function 04 or function 08.
Mode 2 displays operating conditions, for which malfunctions are recognized.
With mode 3 the DTC memory will be checked and with mode 4 the DTC memory will be erased.
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01-10

WARNING!

When performing a road test and checks, the
vehicle diagnostic, testing and information
system VAS5051 as well as the VAG1551
may be secured only on rear seat, from
where it is to be operated by a second
technician.
Please follow safety precautions Page 24
-1

Note:
Only the procedure for OBD VAG1551 is
described below. For details of how to use the
vehicle diagnostic, testing and information
system VAS5051, please refer to its operating
manual. VAG - On Board Dia
gnostic
HELP
1 - Rapid data transfer*2 - Blink code output*

Indicated on display
* Appears alternately
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01-16

No DTC reco
gnized

Indicated on display
or -
Press button.
X DTC reco
gnized

Indicated on display
The stored malfunctions will be displayed and printed out in sequence.
Note: - Locate and eliminate printed out malfunctions according to DTC table
Page 01
-19
.
If no malfunction is stored in the DTC memory, do not erase memory,
otherwise readiness code must be generated. If the DTC memory was erased, generate readiness code Page 01
-
105
.
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01-18

Rapid data transfer DTC Memor
y is erased!

Indicated on display:
Note:
During testing and repair work, malfunctions can be recognized from other
control modules (e.g. disconnected harness connectors). Therefore on
completion, the DTC memories of all control modules must be checked
and erased.
End output -
Press button.- After repairs, check DTC memory again.
Rapid data transfer
HELP
Select function XX

Indicated on display:
- Press buttons -0- and -6- to select function "End Output" and confirm
entry with -Q- button.
Rapid data transfer
HELP
Insert address word XX

Indicated on display:
- Switch ignition off and disconnect diagnostic connector.
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01-19
Diagnostic Trouble Code (DTC) table

Notes:

If malfunctions occur in the sensors and components being monitored, they will be stored in the DTC memory together
with an indication of the type of malfunction. Notes on Engine Power Control (EPC) (drive by wire) Page 24
-139
.
Malfunctions relating to the electronic throttle are also indicated by the EPC (Electronic Power Control) warning light in the
instrument cluster.
Malfunction which decrease exhaust emissions are indicated by an Exhaust Malfunction Indicator Light (MIL), the MIL is
located in the instrument cluster. As soon as certain malfunction are recognized, the MIL is switched on immediately.
There are also malfunctions, were the MIL is switched on only after the engine is started again.
Sporadically occurring malfunctions (temporary malfunctions) will be indicated on the VAG1551 display as "SP."
The DTC table is arranged according to the 5-digit DTC in the left-hand column.
If a malfunction is stored in the DTC memory and then does not occur again during the next 40 engine warm-up phases,
the DTC will be automatically erased.
Components that are indicated as being faulty by the VAG1551 should not be replaced immediately. Always start by
checking the wiring, connectors and Ground (GND) connections for the component using the current wiring diagram. This
is particularly important in the case of sporadic malfunctions (indicated by the letters "SP"on the scan tool display).
If the connector for the engine control module is disconnected or if the battery is disconnected, all the learned values
(adaptation values) stored in the control module will be erased, although the contents of the DTC memory will remain
intact. The next time the engine is started the idling may be rough at first. In this case let the engine run at idle for a few
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