Matching Resistor For Data Bus, Checking

Matching Resistor For Data Bus, Checking

Function
The engine control module communicates with other data bus-compatible control modules.

The control modules are connected via a twisted pair of data bus wires ("high" and "low") and exchange information (messages). Information missing from the data bus will be recognized as a fault by both the engine control module and other data bus control modules.

The data bus requires a matching resistor to function fault free. This central matching resistor is located in the engine control module.

NOTE: You can read out which control modules are actively connected via data bus to the engine control module in measuring value blocks 125 and 126.

Test conditions
- A data bus fault has been recognized by the On Board Diagnostic.

Special tools and equipment
- Test box VAG 1598/31
- Hand multimeter VAG 1526 or multimeter VAG 1715
- Adapter set VAG 1594
- Wiring diagram.

Test sequence
- Remove wiper arms and cowl panel:
- Unlock the engine control module connector and pull it off.
- Connect test box VAG 1598/31 to engine control module. The control module wiring harness is not connected by this action.
- Check centralized matching resistor in engine control module.

- To do this, measure resistance between test box
Sockets 58 + 60
Specification: 60 to 72 Ohms

If the resistance measurement is outside the specified range:
- Replace engine control module.

If the resistance value is within the specified range:
- Check drive train data bus.