GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2007 🢒 VUE - AWD 🢒 Power and Signal Distribution 🢒 Wiring Systems and Power Management 🢒 DTC B1372
Table 1: Device Power Moding

Circuit Description

Normal vehicle class 2 communication will not commence until the system power mode has been identified. The body control module (BCM) communicates the system power mode to all the modules connected to the class 2 serial data circuit. The BCM monitors the state of the ignition 1 voltage circuit, accessory voltage circuit and the engine run flag (ERF) in order to determine the present system power mode. The ERF is a serial data message from the engine controller.

DTC Descriptors

This diagnostic procedure supports the following DTC:

DTC B1372 Device Ignition 1 (Run/Crank) Circuit Low

Conditions for Running the DTC

The only requirements are voltage and ground.

Conditions for Setting the DTC

The BCM has detected the ignition 1 voltage circuit is open or shorted to ground for greater than 1.2 seconds when the accessory voltage circuit is high and the engine run flag is true.

Action Taken When the DTC Sets
    • There is no cluster illumination during bulb check.
    • The malfunction indicator lamp (MIL) is illuminated.
    • BCM (IGN 1) fuse will open with a short to ground present.

Conditions for Clearing the MIL/DTC
    • A current DTC clears and the MIL is turned OFF when the fault is no longer present.
    • A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the fault.

Diagnostic Aids

Refer to Testing for Intermittent Conditions and Poor Connections .

Device Power Moding

Key Position

Ignition Accessory/Run

Ignition 1 Run/Crank

RUN

Active

Active

CRANK

Inactive

Active

ACCY

Active

Inactive

OFF

Inactive

Inactive

Test Description

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

  1. This step tests the inactive signal circuit for an open or a high resistance.

Step

Action

Yes

No

Schematic Reference: Power Moding Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the Ignition 1 Input parameter in body control module (BCM) security data display.

Does the Ignition 1 Input parameter display High?

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the BCM connector C2.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the inactive ignition 1 voltage signal circuit and a ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 5

4

Inspect for poor connections and terminal tension at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 7

Go to Step 6

5

Repair the inactive ignition 1 voltage signal circuit for an open, high resistance or a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you complete the repair?

Go to Step 7

--

6

Replace the BCM. Refer to Control Module References for replacement, setup and programming.

Did you complete the replacement?

Go to Step 7

--

7
  1. Use a 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