Absence of external CAN bus
• Trouble shoot brown CAN bus cable harness and connectors. • Check connector for brown CAN-bus on MBS (pin CN3-14 and 15). • Check wiring for External CAN-bus: - Measure the resistance (with the battery disconnected) between CAN-high (pin CN3-07) and CAN-low (pin CN3-08). It should be close to 60 ohm (one 120 ohm termination resistor in each end of the CAN-bus). - Measure the resistance (with the battery disconnected) between CAN-high on MBSM (pin CN3-07) and CAN-high on any other unit on the brown CAN-bus. It should be close to zero ohm. - Measure the resistance (with the battery disconnected) between CAN-low on MBS (pin CN3-08) and CAN-low on any other unit on the brown CAN-bus. It should be close to zero ohm.
What you'll see
No driver-visible symptom recorded.
System reaction
Function dependent on information from the external CAN are degraded and/or missing in MBS.
Diagnostic depth
The fault is validated as present if the ECU does not detect CAN-messages on the external CAN bus within the timeout period.
• Defect wiring for the external CAN bus. • Defect ECU unit(s) on the external CAN bus.