01-26
The CAN-bus terminates in a resistor. It prevents
the transmitted data from returning as an echo
from the ends and corrupting data.
The terminal resistances of the CAN-bus have a
value of 120 and are located in the ABS
control module (w/EDL) -J104- and the Engine
Control Module (ECM) -item 3-. This results in an
overall terminal resistance of approx. 60 . The steering angle sensor -G85- transmits its
data to the control module via the CAN-bus. It
does not have a terminal resistance.
As of implementation of control module 8D0 907
389 D/E, the CAN-bus is connected centrally in
the Engine Control Module (ECM) with a
resistance of approximately 66 . All other
control modules connected to the CAN system
(for example the ABS control module -J104-) are
connected with a high ohm resistance of 2.6 k .
Pa
ge 2 of 12 CAN-
bus
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01-27
CAN-bus system, checking
The DTC table indicated you needed to check
the bus:
- Using the relevant wiring diagram, determine
how many control modules are connected to the
CAN-bus.
- Check that the multiple connectors of the control
modules are properly connected (unobstructed).
- Connect the VAG1551 (or VAG1552) scan tool
and press the -0- button twice to select the
"Automatic Check" function 00.
- Before checking the bus wires, make sure that
none of the control modules connected have a
function malfunction.
Note:
In this context, a function malfunction means a
malfunction that doesn't directly affect the bus
system, but that interrupts the functioning of a
system. This could be a malfunctioning sensor,
for example. A malfunctioning sensor would
mean that the sensor signal could no longer be
used for data transfer in the bus system. This
type of malfunction indirectly affects the bus
system. Communication to the control modules
Pa
ge 3 of 12 CAN-
bus
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