A6 Quattro Sedan V8-4.2L (BVJ) (2007)
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Control Module: Testing and Inspection
CAN-Bus Terminal Resistance, TCM to ECM, Checking
CAN-Bus Terminal Resistance, TCM to ECM, Checking
The Engine Control Module (ECM) (J623) communicates with all databus capable control modules via a CAN databus.
These databus capable control modules are connected via two data bus wires which are twisted together (CAN_High and CAN_Low), and exchange
information (messages). Missing information on the databus is recognized as a malfunction and stored.
Trouble-free operation of the CAN-bus requires that it have a terminal resistance. The central terminal resistor is located in the Engine Control
Module (ECM) (J623).
Special tools, testers and auxiliary items required
‹› Multimeter.
‹› Wiring diagram.
Test requirement
‹› A CAN-Bus malfunction was recognized.
‹› The Engine Control Module (ECM) (J623) fuses OK.
‹› The Transmission Control Module (TCM) (J217) fuses OK.
‹› Battery voltage at least 12.5 V.
‹› Ignition switched off.
Test procedure
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Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] See: Powertrain Management/Computers and
Control Systems/Testing and Inspection/Scan Tool Testing and Procedures/Preliminary Check.
Start diagnosis
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Disconnect the Transmission Control Module (TCM) (J217) electrical harness connector - direction of the arrow -.
‹› The Engine Control Module (ECM) (J623) must remain connected for the following step.
-
Using a Multimeter, check the Transmission Control Module (TCM) (J217) electrical harness connector terminals 2 to 6 for resistance.
Specified value: 60 to 72 ohms (at approx. 20° C)
If the specified value was not obtained:
