GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The body control module (BCM) monitors the battery positive voltage and battery negative circuit voltage to determine if it is between 9-15 volts and sends this information out as a class 2 message to the vehicle theft deterrent (VTD).

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1327 Device Power Circuit Low

Conditions for Running the DTC

This DTC shall run only if the BCM has power, ground, and the ignition is not in START mode.

Conditions for Setting the DTC

This DTC shall be set as current when the voltage falls below 9 volts for 1.2 milliseconds.

Action Taken When the DTC Sets

A message shall be sent out on the class 2 lines to illuminate the charge indicator and security lamp.

Conditions for Clearing the MIL/DTC

In order to clear the DTC from a current status, the voltage shall be greater than 9.54 volts for 1,200 milliseconds.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests for the proper operation of the complete circuit.

  2. This step tests for the proper operation of the signal input circuit.

Step

Action

Value(s)

Yes

No

Schematic Reference: Theft Deterrent System Schematics in Theft Deterrent

Connector End View Reference: Computer/Integrating Systems Connector End Views in Computer/Integrating Systems

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

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

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

9 V

Go to Step 3

Go to Charging System Test

3

Replace the body control module (BCM). Refer to Control Module References in Computer/Integrating Systems.

Did you complete the replacement?

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Go to Step 4

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4

  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?

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Go to Step 2

System OK