Receiving

Receiving







When a control module transmits, all other control modules listen to it. They do this by looking at the difference in voltage between bus+ and bus-. (A voltage difference close to 0 V is interpreted as a one and a difference close to 5 V as a zero.)

What the various combinations of ones and zeros mean is determined in advance so that all control modules interpret the information identically. The message contains a description of what is sent and its value, e.g. "Coolant temperature 100 degree C or A/C On".

Electrical interference, such as from a relay, will affect the voltage on both leads in the same direction. The difference in voltage will not be affected, however, and this makes the bus extremely insensitive to interference.