Absence of main bus CAN communication (CAN1 buffer overflow)
• Measure the resistance (with the battery disconnected) between CAN-high (pin A12) and CAN-low (pin A9). 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 A12) and supply. It should be high ohmic. • Measure the resistance (with the battery disconnected) between CAN-high (pin A12) and ground. It should be high ohmic. • Measure the resistance (with the battery disconnected) between CAN-low (pin A9) and supply. It should be high ohmic. • Measure the resistance (with the battery disconnected) between CAN-low (pin A9) and ground. It should be high ohmic. • Disconnect one ECU unit at the time from the expansion CAN-bus and check if the fault disappears.
What you'll see
No driver-visible symptom recorded.
System reaction
• Functions dependent on information from expansion CAN bus are degraded.
Diagnostic depth
The DTC is set to active if CAN controller of the external bus is in the state bus-off. The DTC is set to inactive if the CAN-controller is not in state bus-off for 1100 ms. The DTC is not validated (stored) if: • the ignition is turned off • first 2 seconds after ignition on • the supply voltage is below 22 volt • the supply voltage is above 32 volt
• Defect wiring of expansion 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 expansion CAN-bus.