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 or OnStar Schematics Connector End View Reference: Computer/Integrating Systems Connector End Views or Cellular Communication Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
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 |
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 . Did you find and correct the condition? | -- | System OK | -- |
6 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | System OK | -- |
7 | Replace the vehicle control interface module (VCIM/OnStar®). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | System OK | -- |
