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CAN-Bus, Checking Terminal Resistance







CAN-Bus, Checking Terminal Resistance

Function

Control module for Diesel-Direct fuel injection system communicates with other CAN-Bus capable control modules.

These databus-capable components 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. This central terminal resistor is located in the Engine Control Module (ECM).

Special tools, testers and auxiliary items required

• Multimeter (VAG1526) or Multimeter (VAG1715)

• Connector test kit (VAG1594)

• Wiring diagram

Test Prerequisite

• Ignition is switched off.

Test Sequence

- Remove cover -D- for plenum chamber, right side.





- Disengage and disconnect connector - A - of the corresponding Engine Control Module (ECM):





• Cylinder bank 1: Engine Control Module (ECM) (J623) (- 1 -).

• Cylinder bank 2: Engine Control Module 2 (J624) (- 2 -).

• Cylinder bank 1 is located in direction of travel, right.

• Cylinder bank 2 is located in direction of travel, left.

- Connect adapter cable ( (VAG1598/39-2)) to test box ( (VAG1598/42)).

- Connect test box to the corresponding Engine Control Module (ECM). During this, wiring harness to Engine Control Module (ECM) is not connected.

- Check the central termination resistor at the Engine Control Modules (ECM):

- To do this, measure resistance between test box

sockets 66 +89.

Specified value: 115 to 135 ohms

Resistance Value in Range

- Connect adapter cable ( (VAG1598/39-1)) to test box ( (VAG1598/42)).

- Connect test box to the corresponding Engine Control Module (ECM). During this, wiring harness to Engine Control Module (ECM) is not connected.

- Then, measure resistance between test box

sockets 54 +55.

Specified value: 115 to 135 ohms

Resistance Value not in Range

- Replace corresponding Engine Control Module (ECM) => [ Engine Control Modules, Replacing ] Engine Control Modules, Replacing.

Resistance Values in Specified Range

- Eliminate malfunction in Data-Bus wires or in other Data-Bus components according to wiring diagram:
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