U1305

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 is unable to transmit a message for approximately three seconds, U1305 is set and the setting of all other class 2 serial communication DTCs is inhibited.

CONDITIONS FOR RUNNING THE DTC
^ The following diagnostic trouble codes do not have a current status:
^ B1327
^ B1328
^ 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 or high.
^ The above conditions are met for approximately three seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The module inhibits the setting of all other class 2 DTCs.
^ The module uses default values for all parameters received on the class 2 serial data circuit.

CONDITIONS FOR CLEARING THE DTC
^ A current U1305 will clear when a valid class 2 message is detected on the class 2 serial data circuit or at the end of the current ignition cycle.
^ A history U1305 will clear upon receipt of a scan tool Clear DTCs command.

DIAGNOSTIC AIDS
^ This DTC cannot be retrieved with a current status. The diagnosis of a current U1305 is accomplished via the symptom, Scan Tool Does Not Communicate with a Class 2 Device.
^ An intermittent condition is likely to be caused by a short to ground on the class 2 serial data circuit. Use the Scan Tool Does Not Communicate with a Class 2 Device procedure to isolate an intermittent condition.