Terminal Resistance For CAN-Bus, Checking

Diagnostic Procedures


Terminal Resistance for CAN-Bus, Checking

Function

The Engine Control Modules communicate 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 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 corresponding Engine Control Module.

Test Conditions

• A CAN-bus malfunction was recognized via On Board Diagnostic, refer to Repair Manual, Diagnostic mode 3: Check DTC memory.

• Ignition switched off.

Special tools, testers and auxiliary items required

• Hand multimeter (V.A.G 1526) or Multimeter (V.A.G 1715)

• Test adapter kit (V.A.G 1594)

• Wiring diagram

Test Sequence

- Connect test box to the corresponding Engine Control Module, connecting test box for wiring test, refer to Repair Manual, The control module wiring harness is not connected.

- Check central terminal resistance in Engine Control Module:

- Measure resistance between test box sockets 58 +60: Specification: 115 to 135 ohms

If resistance value is not in specified range:

Replace the engine control module.

If resistance value is in specified range:

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

- Erase DTC memory of Engine Control Module => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.

- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.