AUDI A4 1999 B5 / 1.G APB Engine Motronic Syst

01-1


Motronic system, On Board
Diagnostic (OBD)

On Board Diagnostic, technical data


Equipment
The advantages of OBD can only be fully
exploited by using the vehicle diagnostic, testing
and information system VAS5051 or the
VAG1551 scan tool, in operating mode 1 "Rapid
data transfer."
The DTC memory is equipped with a permanent
memory and therefore does not depend on the
power supply.
The stored malfunctions will be displayed after
checking the DTC memory Page 01
-15
.
After eliminating malfunctions the DTC memory
must be erased Page 01
-15
.

Important note:

Every time the DTC memory is erased and the
voltage supply to the Motronic Engine Control
Module (ECM) -J220 has been interrupted the
readiness code must be generated Page 01
-
105
.
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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.
Pa
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01-4

Checking function

- Switch ignition on.

The MIL must light up
If the MIL does not light with ignition switched:

Cause:
MIL is not
activated or does
not light up
because of an
open circuit. Corrective action:
The MIL should light up.
If the MIL does not light up:
If the lamp and the voltage - Switch ignition off
- Connect VAG1598/31 test
box Page 24
-20

- Bridge sockets 2 and 47 on
test box
- Switch ignition on.
- Switch ignition off.
- Check whether lamp is
burned out and test voltage
supply to lamp wiring
diagram.
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supply are OK:
- Check for open circuit or
short circuit in wiring
between engine control
module and MIL using wiring
diagram. Determine and
eliminate malfunction.
If there are no malfunctions in
the wiring to the MIL:
Malfunction
cause: Engine control module (ECM)
faulty Replace Engine
Control Module (ECM)
Page 24
-24
.
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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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reached:
- Determine and eliminate
short circuit to Ground in wiring
between engine control
module and MIL using wiring
diagram.
If there are no malfunctions in
the wiring to the MIL:
Malfunction
cause: Engine control module (ECM)
faulty Replace Engine Control
Module (ECM) Page 24
-24
.
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01-6

Available functions

The prerequisites for selecting the desired
functions can be taken from the following table.
Address words and functions on VAG1551 scan tool
Ignition ON,
engine not running
Engine idling
Vehicle being driven
Address words
00 Automatic Test Sequence yes yes yes
01 Engine Electronics yes yes yes
Functions
01 Check Control Module Version yes yes yes
02 Check DTC Memory yes yes yes
03 Output Diagnostic Test Mode (DTM) yes no no
04 Basic setting yes yes yes
05 Erase DTC Memory yes yes yes
06 End Output yes yes yes
07 Code Control Module no no no
08 Read Measuring Value Block yes yes yes
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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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01-8

Mode 5 displays the static dimensions of the oxygen sensors, which are legally required. Since these dimensions are not
directly relevant to oxygen sensor diagnostics, mode 5 is insignificant for the authorized Audi center.
With mode 6 all measured values can be checked from components and systems that are not constantly monitored.
Using mode 7, DTCs can be checked for which the Malfunction Indicator Light (MIL) is not yet lit (MIL is not on, no DTCs
under mode 3).
Under mode 8 the tank leak test will be checked.
With mode 9 the following vehicle information can be read out: Vehicle Identification Number (VIN), Part number and
program/data level of the engine control module and the check sum (this value is a internal calculated value).
Pa
ge 10 of 166 Motronic s
ystem, On Board Dia
gnostic
(OBD
)
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e=re
pair&id=AUDI.B5.FU04.01.1