Passat Sedan 4Motion W8-4.0L (BDP) (2002)
Engine Control Module: Component Tests and General Diagnostics
Terminal resistance for CAN-Bus, checking
Function
The Engine Control Module (ECM) communicates with all databus-capable control modules via a CAN-Bus.
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 CAN-Bus is recognized as a malfunction and stored.
Trouble-free operation of the CAN-Bus requires that it have a terminal resistance. This central terminal resistor is located in the Engine Control Module
(ECM).
Recommended special tools and equipment
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VAG1526 multimeter or VAG1715 multimeter
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VAG1594 connector test kit
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Wiring diagram
Test requirements
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A CAN-bus malfunction was recognized via On Board Diagnostic (OBD), Diagnostic mode 3: Check DTC memory. See: Testing and
Inspection/Scan Tool Testing and Procedures/Diagnostic Mode 3: Check DTC Memory
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Ignition switched off.
Test sequence
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Connect test box to Engine Control Module (ECM), connect test box for wiring test. During this, wiring harness to Engine Control Module (ECM)
is not connected. See: Testing and Inspection/Reading and Clearing Diagnostic Trouble Codes/Scan Tool Connecting/With Generic Scan
Tool/Test Box, Connecting For Wiring Test
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Check the central termination resistor in the Engine Control Module (ECM).
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To do this, perform a resistance measurement between test box sockets 58 + 60 and 77 + 79:
Specified value: 120...144 Ohms
If resistance value is not in expected range:
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Replace Motronic Engine Control Module (ECM) -J220-.
If resistance value is in expected range:
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Eliminate malfunction in wires or in other Data-Bus components according to wiring diagram.