TT Roadster L4-2.0L Turbo (BPY) (2008)
Control Module: Testing and Inspection
CAN-Bus Terminal Resistance, Direct Shift Gearbox (DSG) Mechatronic J743 to Engine Control
Module (ECM) J623 , Checking
CAN-Bus Terminal Resistance, Direct Shift Gearbox (DSG) Mechatronic J743 To Engine Control Module (ECM) J623, Checking
Special tools, testers and auxiliary items required
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Multimeter.
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Wiring diagram.
Test requirement
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A CAN-Bus malfunction was recognized.
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The Engine Control Module (ECM) J623 Direct Shift Gearbox (DSG) Mechatronic J743 fuses OK.
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The Direct Shift Gearbox (DSG) Mechatronic J743 fuses OK.
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Battery voltage at least 12.5 volts.
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All electrical consumers such as, lights and rear window defroster, switched off.
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Vehicles with automatic transmission, shift selector lever into position "P" or "N".
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A/C switched off.
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Ground (GND) connections between engine/transmission/chassis OK.
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Ignition switched off.
Function
The Engine Control Module (ECM) J623 communicates with other CAN-Bus capable control modules.
The control modules are connected by two data bus wires which are twisted together (CAN_High and CAN_Low), and exchange information
(messages). Missing information on the CAN-bus is recognized as a malfunction by the Engine Control Module (ECM) J623 and the other control
modules connected to the CAN-bus.
Trouble-free operation of the CAN-Bus requires that it have a terminal resistance. This central terminal resistance is located in the Engine Control
Module (ECM) J623.
Test procedure
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Perform a preliminary check to verify the customers complaint.
Start diagnosis
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Disconnect the Direct Shift Gearbox (DSG) Mechatronic J743 electrical harness connector.
NOTE: The Engine Control Module (ECM) J623 must remain connected for the following step.
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Using a Multimeter, check the Direct Shift Gearbox (DSG) Mechatronic J743 electrical harness connector terminals 10 to 15 for resistance.
Specified value: 60 to 72 ohms (at approx. 20 degrees C)
If the specified value was not obtained:
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Check the wiring connection for an open circuit, short circuit to Battery (+) or Ground (GND).
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Check the wiring connection for damage, corrosion, loose or broken terminals.
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If necessary, repair the faulty wiring connection.
If no malfunction is found in the wiring:
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Replace the Engine Control Module (ECM) J623.
If the specified value was obtained:
Checking wiring
If the manufacturers test box is being used. Perform the following step.
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Install the test box.
If the manufacturers test box is not being used. Perform the following step.
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Remove the Engine Control Module (ECM) J623.
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Using a Multimeter, check the Direct Shift Gearbox (DSG) Mechatronic J743 electrical harness connector to the Engine Control Module (ECM)
J623 electrical harness connector T121 for resistance.