CAN-Bus Checking

CAN-Bus, Checking

Function
The Motronic Engine Control Module (ECM) -J220- communicates with other CAN-bus compatible control modules via a CAN-bus.
These CAN-bus-capable components are connected by a pair of twisted CAN-bus wires (CAN high and CAN low) and exchange information (messages). Information missing from the CAN-bus is recognized as an error and stored.
The CAN-bus requires a matching resistor to function Diagnostic Trouble Code (DTC) free. This matching resistor is located in the Motronic Engine Control Module (ECM) -J220-.

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required







- VAG 1551 Scan tool (or VAG 1552) with VAG 1551/3 adapter cable

NOTE: All functions which could previously be performed with VAG 1551/1552 can also be performed with the VAS 5051.

- VAG 1526 Hand multimeter or VAG 1715 multimeter
- VAG 1594 Adapter set
- VAG 1598/31 test box
- Electrical Wiring Diagrams

Test prerequisites
- The CAN-bus On Board Diagnostic (OBD) has detected a Diagnostic Trouble Code (DTC).

Test sequence
- Remove wiper arms and cowl panel:
- Connect VAG 1598/31 test box to Motronic Engine Control Module (ECM) -J220-. The control module wiring harness is not connected by this action.
- Check centralized matching resistor in Motronic Engine Control Module (ECM) -J220-.
- To do this, check resistance between test box
Sockets 58 and 60.
Specification: 60 to 72 ohms

If the resistance measurement are not within the specified range:
- Replace Motronic Engine Control Module (ECM) -J220-.
- Check DTC memory, repair malfunctions if necessary and then erase DTC memory.
Reading Diagnostic Trouble Codes

- Erase learned values and adapt Motronic Engine Control Module (ECM) -J220- again.
- Read readiness code. If the DTC memory has been erased or the Motronic Engine Control Module (ECM) -J220- was disconnected from battery positive (B+), the readiness code must be generated again.
Monitors, Trips, Drive Cycles and Readiness Codes
Monitors, Trips, Drive Cycles and Readiness Codes

If the resistance value is within the specified range:
- Repair Diagnostic Trouble Code (DTC):
- Check DTC memory, repair malfunctions if necessary and then erase DTC memory.
Reading Diagnostic Trouble Codes

- Erase learned values and adapt Motronic Engine Control Module (ECM) -J220- again.
- Read readiness code. If the DTC memory has been erased or the Motronic Engine Control Module (ECM) -J220- was disconnected from battery positive (B+), the readiness code must be generated again.
Monitors, Trips, Drive Cycles and Readiness Codes
Monitors, Trips, Drive Cycles and Readiness Codes