Circuit Description

Modules connected to the class 2 serial data link monitor the link for serial communications during normal vehicle operation. Operating information and commands are exchanged among the modules. In addition to this, Node Alive (State Of Health) messages are transmitted by each module on the class 2 serial data link about once every 2 seconds. When the modules does not detect a message on the Class-II serial data link that it expects to receive, DTC U1255 is set.

Conditions for setting DTC:

• Voltage supplied to module is in the normal operating voltage range (about 9-16 volts).
• Class-II message that module expects to receive is not detected on data link.