GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The BCM has an internal voltage sensor with a dedicated circuit that monitors the battery positive voltage circuit to determine if it is below 18 volts.

Conditions for Running the DTC

This DTC shall run only if no communication codes are set.

Conditions for Setting the DTC

The ignition positive voltage level is greater than 18 volts for approximately 1/2 seconds or more.

Action Taken When the DTC Sets

The BCM sets a DTC and disables the following State of Health (SOH) DTCs:

    • DTC U1096
    • DTC U1255
    • DTC U1300
    • DTC U1301

The BCM illuminates the charge lamp indicator.

Conditions for Clearing the DTC

    • The battery positive voltage level is less than 17.9 volts for approximately 1/2 seconds.
    • A history DTC clears after 100 malfunction free ignition cycles.
    • The BCM receives the clear code command from the scan tool.

Diagnostic Aids

This DTC may set when the vehicle is placed on a battery charger, on fast charge, for a long period of time.

Step

Action

Value(s)

Yes

No

Schematic Reference: Body Control System Schematics in Body Control System

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

  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, observe the Electronics Battery Fd parameter in the BCM data list.

Does the scan tool indicate the battery voltage is greater than the specified value?

18.0 volts

Go to Step 3

Go to Step 4

3

Measure the voltage across the battery terminals.

Is the battery voltage greater than the specified value?

18.0 volts

Go to Charging System Test

Go to Step 4

4

Important: Perform the setup procedure for the BCM. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System.

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

Did you complete the replacement?

--

Go to Step 5

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5

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

 

Go to Step 2

System OK