A4 Sedan L4-2.0L Turbo (BPG) (2005)
Information Bus: Component Tests and General Diagnostics
Terminal Resistance For CAN-Bus, Checking
Terminal Resistance For Can-Bus, Checking
The Engine Control Module (ECM) J623 communicates with all the 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
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Multimeter V.A.G 1526 or equivalent.
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Test Box 105 Pin VAG1598/42.
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Adapter Lead Vag1598/39 VAG1598/39.
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Adapter cable V.A.G 1598/39-1.
Test requirement
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Ignition switched off.
Test sequence
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Connect the Test Box 105 Pin VAG1598/42 to the wiring harness of the Engine Control Module (ECM) J623.
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Check the central termination resistor in the Engine Control Module (ECM) J623.
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Using Multimeter V.A.G 1526 A or equivalent, check the following wiring connection between terminal 58 and 60 of the Test box V.A.G.
1598/31 for resistance.
Specified resistance: 60.......72 Ohms
If the specification is exceeded or not met:
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Replace the Engine Control Module (ECM) J623.
If the specified value is obtained:
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Disconnect the Test Box 105 Pin VAG1598/42 from the Engine Control Module (ECM) J623 wiring harness.
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Connect the Test Box 105 Pin VAG1598/42 to the wiring harness of the Engine Control Module (ECM) J623.
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Using Multimeter V.A.G 1526 A or equivalent, check the following wiring connection between terminals 58 and 60 of the Test Box 105 Pin
VAG1598/42 for resistance.
Specified resistance 1.5 Ohms max.
If the specification is not obtained:
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Check the wiring for a short circuit to Battery positive (+) or an open circuit.
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If necessary, repair the wiring connection.
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1. Check the DTC memory.
2. If necessary, erase the DTC memory.
3. If the DTC memory was erased, generate readiness code.
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End diagnosis and switch the ignition off.