Absence of external CAN bus
• Trouble shoot external CAN bus cable harness and connectors. • Check connector for External 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
Some symptoms: - ICL may not show the correct information about the doors in Bus stop page - CAN buttons on the instrument panel may not work correctly
System reaction
Amber warning for system body fault warning will be shown in the ICL. 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.