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 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.
DTC Descriptors
This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to
DTC Symptom Description .
| • | DTC U1300 Class 2 Data Link Low |
| • | DTC U1301 Class 2 Data Link High |
| • | DTC U1305 Class 2 Data Link Low or High |
DTC Symptom
| DTC Symptom Description
|
00
| No additional information
|
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 in one of the following conditions: |
| • | The above conditions are met for approximately 3 seconds. |
Action Taken When the DTCs Sets
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 can be retrieved with a current status from engine control module (ECM) for LY7 and LP1 types only, because these ECMs communicate functionally on both class 2 and high speed GMLAN serial data circuits, but the communication with
the scan tool is via high speed GMLAN. Diagnosis of current DTC is accomplished via the symptom, Scan Tool Does Not Communicate with a Class 2 Device. Refer to
Scan Tool Does Not Communicate with Class 2 Device . |
| • | An intermittent condition is likely to be caused by a short on the class 2 serial data circuit. Use the Scan Tool Does Not Communicate with a Class 2 Device procedure in order to isolate an intermittent condition. Refer to
Scan Tool Does Not Communicate with Class 2 Device . |
