Terminal Resistance For CAN-Bus, Checking

Terminal Resistance For CAN-Bus, Checking

Function
The Engine Control Module (ECM) communicates with all CAN-Bus-capable control modules via a CAN-Bus.

These CAN-Bus-capable control modules are connected via two CAN-Bus wires which are twisted together (CAN_High and CAN_Low), and exchange information (messages). Missing information on the CAN-Bus 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).

Recommended special tools and equipment
- V.A.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 connector test kit
- Wiring diagram

Test requirements
- A CAN-Bus malfunction was recognized via On Board Diagnostic (OBD), Diagnostic mode 3: Check DTC memory. Diagnostic Mode 03 - Read DTC Memory
- Data Bus On Board Diagnostic Interface -J533- must be OK.
- Ignition switched off.

Test sequence
Observe safety precautions.
Observe rules for cleanliness.

- Connect 94-pin connector of test box to Engine Control Module (ECM), connecting test box for wiring test. Test Box, Connecting For Wiring Test

Harness connectors of control module wiring harness are not connected for this.

Checking terminal resistance
- Check terminal resistance in Engine Control Module (ECM) between sockets 67 and 68 of test box.

Specified value: 60.0...72.0 ohms

If specified value is not obtained:
- Replace Engine Control Module (ECM) -J623-.

If specified value is obtained:
- Eliminate malfunction in CAN-Bus wires or in other CAN-Bus components according to wiring diagram.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes