Terminal Resistance For CAN-Bus, Checking

Terminal Resistance For CAN-Bus, Checking

Function
The Engine Control Module (ECM) communicates with other CAN-bus capable control modules.

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 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 requirement
- Ignition is switched off.

Test sequence







- Remove E-Box cover.







- Unclip retaining bracket for Engine Control Module (ECM).
- Disengage connector from control module and disconnect.
- Connect adapter cable (V.A.G 1598/39-2) to test box (V.A.G 1598/42).
- Connect test box to Engine Control Module (ECM). During this, wiring harness to Engine Control Module (ECM) is not connected.
- Check central termination resistor in the Engine Control Module (ECM):
- To do this, measure resistance between test box sockets 66 + 89.
Specified value: approx. 60 to 72 Ohms

If resistance value is not within specified range:
- Replace Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248-.

If resistance values are in specified range:
- Eliminate malfunction in Data-Bus wires or in other Data-Bus components according to wiring diagram.