check engine AUDI A4 1999 B5 / 1.G AWM Engine Additional Signals Checking User Guide

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Data transfer between Engine Control
Module (ECM) and CAN-bus capable
control modules, checking


Notes:

Data exchange between individual control
modules occurs via a bus system.
The term "CAN-bus" refers to a system that
transports and distributes data.
The wire connections between the control
modules, via which data is transferred, are
referred to as data wires.
Data is transferred to the connected control
modules serially (one after the other) via these
data wires (i.e. engine speed, accelerator
position).

Checking bus system
The DTC table suggested checking the data
exchange between the Engine Control Module
(ECM) and CAN capable control modules.

- Connect VAS5051 tester Page 01
-7 and
select vehicle system "01 - Engine electronics".
Ignition must remain switched on for this.
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Display on VAS5051:
- Check indications in display fields -1- through -4-.
CAN capable control modules connected to the Engine Control Module
(ECM) are indicated:

No indication: 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
-
Press button to change into display group 126.
- Check under display group 126 in the same manner.
-
Press "08 - erase DTC memory" to end function -button.

Display on VAS5051:
- Select diagnostic function "06 - end output" in selection -1-.
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Display on VAS5051:
When a control module responds with its identification, the display
indicates the number of stored errors or indicates "no malfunctions
recognized".
DTCs stored in the system are indicated in sequence and printed out.
Then the VAG1551 scan tool sends the next address word.
If a malfunction related to the"powertrain databus" or the "CAN-bus" is
indicated:
If the correct control modules are installed: - In selection -1-, press diagnostic function "00 - Check DTC memory -
complete system".

DTC memory of all OBD capable systems in the vehicle will be
checked.
- Check whether the Engine Control Module (ECM) and other CAN
capable control modules installed are appropriate for this vehicle (part
no. and coding).
- Check to be sure the multi-pin connectors of the control modules are
securely connected.
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