Fault Symptoms And Diagnosis

When communication hard faults occur on the Automotive Ethernet bus circuits, such as a short to ground or short to power, typically the vehicle will experience a no crank/no start with the MIL illuminated. U-codes may be found in any of the modules on the bus. Check power, ground, the connector, and both bus circuits to the suspect module before replacing the module. If communication on an entire network or networks is not possible, ensure the scan tool is functioning properly and operating with the latest software level.

There are several faults that can interrupt normal operation of the Automotive Ethernet communication network. The network wire may chafe, resulting in one or both wires shorting to chassis ground, shorting to power, or shorting to each other. Damage to a connector can result in the same faults. If either CAN (+) or CAN (-) is shorted to ground, voltage, or together at any place in the circuit, communication is not possible. When an open occurs in the circuit, any module downstream of the open will not communicate. It is possible for a module to fail, resulting in loss of communication with that particular module. If internally shorted, a module fault may bring the whole network down, resulting in no communication on the entire Automotive Ethernet network. If this type of concern occurs, typically the network will begin to communicate normally if the faulty module is disconnected. Remember to verify power and ground, as well as connector faults, before replacing any module.