U1300

CIRCUIT DESCRIPTION
Modules connected to the class 2 serial data circuit monitor for serial data 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 circuit about once every two seconds. When the module detects no messages and a low voltage on the class 2 serial data circuit for approximately three seconds, U1300 is set and the setting of all other class 2 serial communication DTCs is inhibited.

CONDITIONS FOR RUNNING THE DTC
^ Voltage supplied to the module is in the normal operating voltage range (approximately 9 to 16 volts).
^ The vehicle power mode (ignition switch position) requires serial data communication to occur.

CONDITIONS FOR SETTING THE DTC
No valid messages are detected on the class 2 serial data circuit.
^ The voltage level detected on the class 2 serial data circuit is low.
^ The above conditions are met for approximately three seconds.