GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Impala 🢒 Restraints 🢒 SIR 🢒 DTC B1440

Circuit Description

The body control module (BCM) monitors the Ignition 0, Ignition 1 and the accessory signals from the ignition switch. The BCM uses the voltage state (B+ or 0) and the sequence of state changes to determine the power mode called for by the ignition switch.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1440 Power Mode Master Input Circuits Mismatch

Conditions for Running the DTC

The BCM must be powered and must detect a change in the ignition switch circuit states.

Conditions for Setting the DTC
    • One of the ignition switch circuits may be shorted to either B+ or ground.
    • The sequence of the change of the circuit is incorrect for the expected power mode.

Action Taken When the DTC Sets
    • The BCM stores the DTC B1440 to memory.
    • The BCM operates in a fail-safe power mode dependent on the last valid power mode detected and the state of the engine run flag data on the class 2 serial data communications circuits.
    • The other modules on the vehicle operate in a fail safe power mode dependent on the last valid power mode transmitted by the BCM and the state of the engine run flag on the class 2 serial data communications circuits.

Conditions for Clearing the DTC
    • A current DTC clears when the malfunction is no longer present.
    • A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat 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 the ignition switch OFF.
  3. With a scan tool, monitor the following in Body Control Module (BCM), Data Display, Inputs:
    4. • Ignition 0
    • Ignition 1
    • Accessory Switch

Does the scan tool indicate that all inputs are OFF/Inactive?

Go to Step 3

Go to Step 7

3
  1. Turn the ignition switch to ACCESSORY.
  2. With a scan tool, monitor the following in BCM, Data Display, Inputs:
    3. • Ignition 0
    • Ignition 1
    • Accessory Switch

Does the scan tool indicate that the Ignition 0 and Accessory Switch inputs are Active?

Go to Step 4

Go to Step 9

4
  1. Turn the ignition switch to ON, with the engine OFF.
  2. With a scan tool, monitor the following in BCM, Data Display, Inputs:
    3. • Ignition 0
    • Ignition 1
    • Accessory Switch

Does the scan tool indicate that the Ignition 0, Ignition 1 and the Accessory Switch inputs are ON/Active?

Go to Step 5

Go to Step 9

5

Important: The engine may start in this step. Turn the engine OFF immediately after reviewing the input data.

  1. Turn the ignition switch to CRANK/START.
  2. With a scan tool, monitor the following in BCM, Data Display, Inputs:
    3. • Ignition 0
    • Ignition 1
    • Accessory Switch

Does the scan tool indicate that the Ignition 0 and the Ignition 1 inputs are Active?

Go to Step 6

Go to Step 9

6

Were any of the ignition switch inputs active when they were not called for in the previous steps?

Go to Step 7

Go to Step 12

7
  1. Disconnect the ignition switch harness connectors.
  2. Install a scan tool.
  3. With a scan tool, monitor the following in BCM, Data Display, Inputs:
    4. • Ignition 0
    • Ignition 1
    • Accessory Switch

Does the scan tool indicate that any of the Ignition 0, Ignition 1 and the Accessory Switch inputs are ON/Active?

Go to Step 8

Go to Step 10

8
  1. Disconnect the BCM harness connectors.
  2. Test the suspect ignition switch input circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 12

9
  1. Disconnect the ignition switch connectors.
  2. Install a 3-amp fused jumper between the suspect circuits and an ignition switch B+ supply.
  3. With a scan tool, monitor the suspect circuits in BCM, Data Display, Inputs.

Does the scan tool indicate that the suspect circuits is now ON/Active?

Go to Step 10

Go to Step 11

10

Inspect for poor connections at the ignition switch harness connectors. 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 15

Go to Step 13

11
  1. Disconnect the BCM harness connectors.
  2. Test the suspect ignition switch input circuits for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 12

12

Inspect for poor connections at the BCM harness connectors. 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 15

Go to Step 14

13

Replace the ignition switch. Refer to Ignition and Start Switch Replacement in Instrument Panel, Gages, and Console.

Did you complete the replacement?

Go to Step 15

--

14

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

Did you complete the replacement?

Go to Step 15

--

15
  1. Reconnect all components.
  2. Use the scan tool in order to clear DTCs.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

System OK

Go to Step 2