The CAN network allows control units to share information over a pair of wires. The engine, ABS, instrument cluster, steering, climate control and many other modules depend on this communication.
A short circuit, corrosion, poor ground or faulty control unit can block the entire network. The result may be numerous faults, a no-start condition or loss of communication with several systems.
Diagnosis requires measuring signals, resistance and voltage, studying vehicle topology and disconnecting components in a controlled way. Replacing the first module listed in the fault memory is rarely reliable.
Once the point distorting the network is found, many apparently unrelated faults can disappear together.
