Circuit Description
The Class 2 serial data line is used to communicate information between modules. Each module connected to the serial data line is assigned its own recognition code (address). This code is used to identify which modules are communicating. Modules communicate with each other by periodically sending State of Health (SOH) messages. When the ignition switch is in RUN, each module communicating on the serial data line sends a State of Health (SOH) message every two seconds to ensure that the system is operating properly. This module also monitors the serial data line for a short to ground or voltage condition. If the module detects a short to ground for more than 3.0 seconds, no communication will be established between this module and other modules. This module stores the Class 2 Bus Shorted to Ground DTC U1300.
Conditions for Setting the DTC
| • | DTC U1300 only sets if DTC B1328, B1327, B1982 or B1983 is not current in module memory. |
| • | The module detects that the Class 2 serial data line is shorted to ground for at least 3 seconds. |
Action Taken When the DTC Sets
| • | DTC U1300 is stored in module memory. |
| • | The module uses the default values for any information needed from the other modules on the Class 2 serial data line. |
| • | This DTC does not cause a driver warning message to appear. |
Conditions for Clearing the DTC
| • | This DTC clears (status changes from current to history) when the module detects the Class 2 bus is not shorted to ground. |
| • | A history DTC clears after 50 consecutive ignition cycles if the conditions for setting the DTC are no longer present. |
| • | Use the On-Board clearing DTCs feature. Refer to Diagnostic Trouble Code (DTC) Clearing in HVAC Systems with A/C - Automatic. |
| • | Use a scan tool. |
Diagnostic Aids
This DTC is never received as current because the Class 2 serial data line does not function during this condition.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
Perform the Body Control Module Diagnostic System Check before continuing with the diagnosis of this DTC.
-
Check CKT 1807 (PPL) for intermittent shorts to ground.
-
Clear all DTCs after the repair procedure is complete.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Body Control Module Diagnostic System Check performed? | -- | |||
Using the scan tool monitor Class 2, while moving the harness. Is there a Class 2 problem indicated? | -- | |||
3 | Repair the short to ground in CKT 1807. Did you complete the repair? | -- | ||
Are all DTCs cleared? | -- | -- |
