Absence of FMS bus CAN communication (CAN4 buffer overflow)
• Check connector for FMS CAN-bus on BCI (pin C20 and C17). • Check wiring for FMS CAN-bus: - Measure the resistance (with the battery disconnected) between CAN-high (pin C20) and CAN-low (pin C17). 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 BCI (pin C20) and CAN-high on any other unit on the FMS CAN-bus. It should be close to zero ohm. - Measure the resistance (with the battery disconnected) between CAN-low on BCI (pin C17) and CAN-low on any other unit on the FMS CAN-bus. It should be close to zero ohm. • Check wiring and connector for the ignition signal (pin A11) on the BCI.
What you'll see
No driver-visible symptom recorded.
System reaction
• Functions dependent on information on the FMS CAN-bus from BCI might be degraded.
Diagnostic depth
The fault is validated as present if the ECU tries to send CAN-messages on the FMS CAN-bus, but no acknowledge is received from other units, and thereby causing the internal send buffer (in the ECU) to overflow. The DTC is set to active if the buffer overflow has lasted for 50 ms. The DTC is set to inactive when the CAN-messages are sent properly again and the buffer no longer is overflowing for the last 1050 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 • short circuit on FMS CAN-bus (separate DTC)
• Defect connectors on BCI for FMS CAN-bus (pin C20 or C17). • Defect wiring for FMS CAN-bus, open circuit on CAN-high (pin C20) or CAN-low (pin C17). • Ignition signal (pin A11) on BCI is short circuit to supply.