GM Service Manual Online
For 1990-2009 cars only

Object Number: 324022  Size: MF
Body Control Module Components
Body Control System Schematics

Circuit Description

The Class 2 serial data line communicates information between the modules. Each module connected to the serial data line is assigned a recognition code, or address. This code is used in order 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 that is communicating on the serial data line sends an SOH message every 2 seconds. This ensures that the system is operating properly. The module also monitors the serial data line for short to ground. If the module detects a short to ground for more than 3.0 seconds, the module stores the Class 2 Bus Shorted to Ground DTC U1300.

Conditions for Setting the DTC

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 the memory module.
    • 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.
    • Current and history DTCs may be cleared manually by using a scan tool.

Diagnostic Aids

This DTC is not 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 in the diagnostic table.

  1. Inspect CKT 1807 (PPL) for intermittent shorts to ground.

  1. Clear all DTCs after you complete the repair.

Step

Action

Value(s)

Yes

No

1

Did you perform the Data Link Communications Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Data Link Communications

2

Attempt to establish communication with all of the modules using a scan tool.

Does the scan tool communicate with all of the modules?

--

Go to Step 3

Go to the appropriate diagnostic system check

3

Repair the intermittent short to ground in the Class 2 serial data line CKT 1807 (PPL).

Did you complete the repair?

--

Go to Step 4

--

4

  1. Turn the ignition switch to OFF.
  2. Reconnect or install any connectors or components that were disconnected or removed.
  3. Turn in the ignition switch.
  4. Clear any DTCs.

Are all of the DTCs cleared?

--

Go to Diagnostic System Check - Data Link Communications

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