U1301

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. Node Alive messages are transmitted by each module on the class 2 serial data circuit about once every 2 seconds. When the module detects one of the following conditions on the class 2 serial data circuit for approximately 3 seconds, the setting of all other class 2 serial communication DTCs is inhibited and a DTC will set.

CONDITIONS FOR RUNNING THE DTCs
^ Voltage supplied to the module is in the normal operating voltage range.
^ The vehicle power mode requires serial data communication to occur.

CONDITIONS FOR SETTING THE DTCs
^ No valid messages are detected on the class 2 serial data circuit.
^ The voltage level detected on the class 2 serial data circuit is under one of the following conditions:
- High
- Low
^ The above conditions are met for approximately 3 seconds.

ACTION TAKEN WHEN THE DTCs 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 DTC clears when the malfunction is no longer present.
^ A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

DIAGNOSTIC AIDS
^ These DTCs cannot be retrieved with a current status. Diagnosis of current DTCs is accomplished via the symptom. Refer to Scan Tool Does Not Communicate with Class 2 Device. Symptom Related Diagnostic Procedures
^ An intermittent condition is likely to be caused by a short or an open on the class 2 serial data circuit. Use the Scan Tool Does Not Communicate with Class 2 Device procedure in order to isolate an intermittent condition. Symptom Related Diagnostic Procedures