Electrical error on external CAN bus
• Measure the resistance (with the battery disconnected) between CAN-high (pin C14) and CAN-low (pin C15). 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 (pin C14) and supply. It should be high ohmic (Mega ohm). • Measure the resistance (with the battery disconnected) between CAN-high (pin C14) and ground. It should be high ohmic (Mega ohm). • Measure the resistance (with the battery disconnected) between CAN-low (pin C15) and supply. It should be high ohmic (Mega ohm). • Measure the resistance (with the battery disconnected) between CAN-low (pin C15) and ground. It should be high ohmic (Mega ohm). • Disconnect one ECU unit at the time from the external CAN-bus and check if the fault disappears.
What you'll see
No driver-visible symptom recorded.
System reaction
• Functions dependent on information from external CAN bus are degraded.
Diagnostic depth
Communication error. The CAN-controller of the external CAN-bus has entered state bus-off. There is a short circuit on the external CAN-bus
• Defect wiring of external CAN-bus: - short circuit between CAN-high and CAN low. - short circuit between CAN-high and supply voltage. - short circuit between CAN-high and ground. - short circuit between CAN-low and supply voltage. - short circuit between CAN-low and ground. • Defect ECU unit(s) on the external CAN-bus.