For CAN-Bus, Checking
The Engine Control Module (ECM) communicates with all databus-capable control
modules via a CAN databus.
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
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
- A CAN-Bus malfunction was recognized via On Board Diagnostic (OBD).
Diagnostic mode 3: Check DTC memory.
- Ignition switched off.
- Connect test box to Engine Control Module (ECM). connect test box
for wiring test. During this, wiring harness to Engine Control Module
(ECM) is not connected.
- Check the central termination resistor in the Engine Control
- To do this, measure resistance between test box socket 58 + 60:
value: 60.0 to 72.0 Ohms
If resistance value is not in specified range:
- Replace Motronic Engine Control Module (ECM)
If resistance value is in specified range:
- Disconnect test box harness connector from Engine Control Module
- Connect test box to control
module wiring harness.
- Check CAN data bus wires for shorts among one another:
- To do this, perform a resistance measurement between test box
sockets 58 + 60:
Specified value: Infinite Ohms
If specified value is obtained (wires have no shorts):
- Eliminate malfunction in Data-Bus wires or in other Data-Bus
components according to wiring diagram.