With Manufacturer's Scan Tool

CAN-bus, checking

Function
The Diesel Direct Fuel Injection Engine Control Module -J248- communicates with all control modules capable of data bus via CAN data bus.

Data bus-compatible control units are connected together via two data bus wires twisted together (CAN high and CAN low) and exchange information (messages). Information not available in the data bus will be recognized as a fault by the engine control unit as well as other CAN data bus control units.

The data bus requires a matching resistor to function fault free. This central matching resistor is located in the Diesel Direct Fuel Injection Engine Control Module -J248-.

Further information: Self study program No. 186 "The CAN data bus".

Test conditions
A malfunction has been recognized by the CAN data bus On Board Diagnostic (OBD)

Special tools, test equipment and auxiliary items
- Test box VAG 1598/31
- Hand multimeter VAG 1526 or multimeter VAG 1715
- Adapter set VAG 1594
- Wiring diagram

Test sequence
- Switch off ignition.
- Remove wiper arms and plenum chamber cover.
- Unlock the Diesel Direct Fuel Injection Engine Control Module connector and pull it off
- Connect test box VAG 1598/31 to Diesel Direct Fuel Injection Engine Control Module -J248-. The control module wiring harness is not connected by this action.
- Check end resistor in engine control unit.
- Perform a resistance measurement between test box sockets:
Sockets 6 + 7
Specification: 60 to 72 ohms

If the resistance value is outside the specified range:
- Replace Diesel Direct Fuel Injection Engine Control Module -J248-

If the resistance value is within the specified range:
- Repair the malfunction in the wiring using wiring diagram:
- Check DTC memory and, if necessary, repair any malfunctions and then erase.
- Read-out the readiness code. If the DTC memory has been erased or the Diesel Direct Fuel Injection Engine Control Module -J248- was disconnected from permanent battery positive (B+), the readiness code must be generated again.