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With Manufacturer's Scan Tool



CAN-Bus, Checking

Function
The Motronic Engine Control Module (ECM) -J220- communicates with all data-bus capable control modules via a CAN-bus.

The data-bus capable control modules are connected and exchange information (messages) via two data-bus wires (CAN-High and CAN-Low) that are twisted to each other. Missing information on the data-bus is recognized as a malfunction by the Motronic Engine Control Module (ECM) -J220- as well as by other CAN-bus control modules.

The data-bus requires an adapting resistor to function fault-free. This central adapting resistor is located in the Motronic Engine Control Module (ECM) -J220-.

Diagnosis via the CAN-bus wire is undertaken via the diagnostic interface for data-bus -J533- in the "Gateway".


NOTE: Control modules which are actively connected via data bus to the Motronic Engine Control Module (ECM) -J220- can be read in measured value blocks 125 and 126.


Further information:
See Self Study Program "The CAN data bus".

Special tools and equipment
- VAG 1598/31 test box
- Multimeter (Fluke 83 or equivalent)
- VW 1594 adapter set
- Electrical Wiring Diagram

Test conditions
- Malfunction has been recognized by Data Bus On Board Diagnostic (OBD)







- All fuses must be OK
- Battery voltage must be at least 11.5 V
- All electrical accessories, e.g. lights and rear window defroster must be switched off
- Air conditioner must be switched off
- Selector lever of the automatic transmission must be in "P" or "N" position

Test sequence
- Switch off ignition.
- Unlock Motronic Engine Control Module (ECM) -J220- connector and disconnect it.
- Connect VAG 1598/31 test box to Motronic Engine Control Module (ECM) -J220-. Control module wiring harness is not connected by this action.
- Check centralized adapting resistor in Motronic Engine Control Module (ECM) -J220- by performing a resistance measurement between test box
Sockets 58 + 60

Specification: 60 to 72 Ohms

If the resistance value is outside the specified
range:
- Replace Motronic Engine Control Module (ECM) -J220-.

If the resistance value is within the specified range:
- Check CAN-Bus wiring using Electrical Wiring Diagram.
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