GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The body control module (BCM) determines battery positive voltage through the 10A Cluster/BCM fuse input. The BCM then sends a class 2 serial data message containing the measured battery voltage value. The vehicle control interface module (VCIM/OnStar®) module monitors this class 2 message to determine vehicle voltage.

Conditions for Running the DTC

    • The ignition in not in START mode.
    • DTC B1390 is not set current.
    • No communication faults are current.

Conditions for Setting the DTC

    • This DTC shall be set as current when the voltage read from the class 2 message falls below 9.0 volts for 1200 milliseconds.
    • When the vehicle exits START the VCIM/OnStar® shall delay checking the class 2 voltage message for 2 seconds.

Action Taken When the DTC Sets

The VCIM/OnStar® will illuminate the OnStar Statues LED.

Conditions for Clearing the MIL/DTC

In order to clear the DTC from a current status the class 2 voltage message shall be greater than 9.54 volts for 1200 milliseconds.

Step

Action

Values

Yes

No

Schematic Reference: Body Control System Schematics in Body Control System or OnStar Schematics in Cellular Communication

Connector End View Reference: Body Control System Connector End Views in Body Control System or Cellular Communication Connector End Views in Cellular Communication

1

Did you perform the Engine Electrical Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - Engine Electrical

2

Measure the voltage across the battery terminals.

Is the battery voltage greater the specified value?

11 V

Go to Step 3

Go to Charging System Test

3

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Electronic Battery FD parameter in the body control module (BCM) data list.

Does the scan tool indicate the battery voltage is equal to the specified value?

B+

Go to Step 7

Go to Step 4

4

Measure the voltage between the BCM battery positive voltage circuit supplied by the 10A Cluster/BCM fuse and ground.

Does the voltage equal the specified value?

B+

Go to Step 6

Go to Step 5

5

Test battery positive voltage circuit supplied by the 10A Cluster/BCM fuse to the BCM for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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System OK

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6

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Did you complete the replacement?

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System OK

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7

Replace the vehicle control interface module (VCIM/OnStar®). Refer to Communication Interface Module Replacement in Cellular Communication.

Did you complete the replacement?

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System OK

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