DTC U1300 Class 2 Data Link Low. Buick GL7 (Export) 2000

For 1990-2009 cars

### 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. 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 - 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.

### 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 U1300 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 U1300 will clear upon receipt of a scan tool Clear DTCs command.

### Diagnostic Aids

• | This DTC cannot be retrieved with a current status. Diagnosis of an U1300 is accomplished via the symptom, Scan Tool Does Not Communicate with Class 2 Device .

• | An intermittent condition is likely to be caused by a short to ground on the class 2 serial data circuit. Refer to Scan Tool Does Not Communicate with Class 2 Device in order to isolate an intermittent condition.