Absence of Red bus communication (CAN1 buffer overflow)
• Check connector for red CAN-bus ion COO (pin B1 and B10). • Check wiring for red CAN-bus: - Measure the resistance (with the battery disconnected) between CAN-high (pin B1) and CAN-low (pin B10). 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 COO (pin B1) and CAN-high on any other unit on the red CAN-bus (e.g. EMS). It should be close to zero Ohm. - Measure the resistance (with the battery disconnected) between CAN-low on COO (pin B10) and CAN-low on any other unit on the red CAN-bus (e.g. EMS). It should be close to zero Ohm. • Check wiring and connector for the ignition signal (pin A1) on the COO. • Check that no third party controller/instrument is installed. • Check connectors for all ECU:s on the indicated bus. Check for verdigris, broken, unconnected or shorted pins. Disconnect one ecu at a time.
What you'll see
No driver-visible symptom recorded.
System reaction
• Functions dependent on information on red CAN-bus from COO might be degraded. Examples listed below. - engine start - engine control with accelerator pedal
Diagnostic depth
Communication error. Red CAN-bus buffer overflow. The red CAN-bus has an open circuit or a short circuit.
• Defect connectors on COO for red CAN- bus (pin B1 or B10). • Defect wiring for red CAN-bus, open circuit on CAN-high (pin B1) or CAN-low (pin B10). • Ignition signal (pin A1) on COO is short circuit to supply. • Short circuit between CAN-high and supply voltage. • High busload • Defect ECU unit(s) on the red CAN-bus.