Jetta GLS VR6 V6-2.8L (AFP) (2001)
Engine Control Module: Testing and Inspection
CAN-Bus, Checking
With Manufacturer's Scan Tool
Vehicles with automatic gearbox
Function
The Engine Control Module (ECM) communicates with the transmission control module via a CAN data bus.
The CAN-Bus capable control modules are connected via two data bus wires (CAN_High and CAN_Low) which are twisted together (twisted pair) and
exchange information (messages). Information missing on the data bus will be recognized as a malfunction by the Engine Control Module (ECM) and
the transmission control module.
The CAN-Bus requires a matching resistor of 66 ohms to function correctly. This matching resistor is located in the Engine Control Module (ECM).
Special tools and equipment
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VAG1598/18 test box
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VAG1598/31 test box
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Multimeter (Fluke 83 or equivalent)
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VW1594 adapter set
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Wiring diagram
Test requirement
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A malfunction has been recognized by the CAN-Bus On Board Diagnostic (OBD).
Test sequence
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Remove wiper arms and plenum chamber cover.
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Connect VAG1598/31 test box to Engine Control Module (ECM) wiring harness. Engine Control Module (ECM) is not connected by this action.
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Check centralized matching resistor in Engine Control Module (ECM) by measuring resistance between test box sockets 77 + 79.
Specified value: 60-72 ohms
If the resistance measurement is outside the specified range:
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Replace Engine Control Module (ECM). See: Service and Repair
If the resistance measurement is within the specified range:
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Disconnect VAG1598/31 test box from Engine Control Module (ECM).
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Connect VAG1598/31 test box to Engine Control Module (ECM) wiring harness. Engine Control Module (ECM) is not connected by this action.
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Disconnect harness connector (arrow) from transmission control module.
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Check CAN-Bus wiring for short to one another.