Reception, P and I busses (2 lead)

/ 9-5 (9600) / 2006 / 3. Electrical System / Bus and diagnostics communication / Technical description / Reception, P and I busses (2 lead)

When a control module transmits, all the other control modules listen. The control modules listen by sensing the voltage difference between bus+ and bus -. A difference close to 0V is interpreted as a one and a difference close to 5V as a zero.

Appropriate combinations of ones and zeroes are transmitted according to a predetermined protocol so that all the control modules interpret the information in the same way. The message conveys what is being transmitted and the value thereof; e.g. ”Coolant temperature 100°C”, or ”A/C ON”.

Any electrical interference, e.g. from a relay, will cause the voltage on both leads to change in the same direction. The voltage difference is however unaffected and in this way the busses are very resistant to interference.

Reception, P and I busses (2 lead)

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