GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 Equinox 🢒 Vehicle Control Systems 🢒 Computer/Integrating Systems 🢒 Power Mode Mismatch

Circuit Description

The body control module (BCM) is the power mode master responsible for sending the power mode message on the data buses. The BCM monitors Ignition 1 (Run/Crank), Ignition 2 (Acc/Run) and Ignition 3 (Run) signals from the ignition switch, and the engine run flag (ERF) in order to determine the present power mode. Refer to Body Control System Description and Operation for the applicable power mode look up table.

Test Description

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

  1. This step tests for battery voltage on the signal circuits that are not required.

    2.

  2. This step tests for no battery voltage on the required signal circuits.

    3.

  3. If any ignition switch parameters that should be inactive in the present ignition switch position are active, 2 ignition switch signal circuits may be shorted together.

    4.

  4. This step eliminates open circuits as the cause of the malfunction.

Step

Action

Yes

No

Schematic Reference: Body Control System Schematics

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

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Install a scan tool.
  2. Turn OFF the ignition.
  3. With a scan tool, under the Diagnostic Circuit Check menu observe the Class 2 Power Mode parameter.

Does the scan tool display Off Awake or RAP?

Go to Step 3

Go to Step 6

3
  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, under the Diagnostic Circuit Check menu observe the Class 2 Power Mode parameter.

Does the scan tool display Run?

Go to Step 4

Go to Step 6

4

Important:: The engine may start during this procedure. Turn the ignition OFF after verifying this power mode.

  1. Turn the ignition switch to the CRANK position.
  2. With a scan tool, under the Diagnostic Circuit Check menu observe the Class 2 Power Mode parameter.

Does the scan tool display Crank?

Go to Step 5

Go to Step 6

5
  1. Turn the ignition switch to the ACC position.
  2. With a scan tool, under the Diagnostic Circuit Check menu observe the Class 2 Power Mode parameter.

Does the scan tool display Accessory?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 6

6

Important:: The engine may start during this procedure. Turn the ignition OFF after verifying this power mode.

  1. Turn OFF the ignition.
  2. Disconnect the body control module (BCM).
  3. Hold the ignition switch in the position that indicated the incorrect power mode.
  4. With a test lamp attached to a good ground, test the BCM ignition switch inputs for voltage.

Is voltage present on only the inputs specified for the ignition switch position?

Go to Step 7

Go to Step 8

7

Important:: The engine may start during this procedure. Turn the ignition OFF after verifying this power mode.

  1. Hold the ignition switch in the position that indicated the incorrect power mode.
  2. With a test lamp attached to a good ground, test the BCM ignition switch inputs for voltage.

Is voltage not present on any inputs specified for the ignition switch position?

Go to Step 9

Go to Step 11

8

  1. Disconnect the ignition switch.
  2. Test the BCM ignition switch input circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
  3. Test the BCM ignition switch circuits for a short between circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 10

9

  1. Disconnect the ignition switch.
  2. Test the BCM ignition switch input circuits for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 10

10

Inspect for poor connections and terminal tension at the harness connector of the ignition switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 12

11

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 13

12

Replace the ignition switch. Refer to Ignition and Start Switch Replacement in Steering Wheel and Column.

Did you complete the replacement?

Go to Step 14

--

13

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

Did you complete the replacement?

Go to Step 14

--

14

Important:: The engine may start during this procedure. Turn the ignition OFF after verifying all power modes.

  1. Reconnect all disconnected components.
  2. With a scan tool, under the Diagnostic Circuit Check menu observe the Class 2 Power Mode parameter.
  3. Cycle the ignition switch through all possible positions one at a time.

Does the displayed power mode parameter match the actual ignition switch position?

System OK

Go to Step 2