GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2001 🢒 Century 🢒 DTC 🢒 DTC B1422

Circuit Description

The body control module (BCM) monitors the Ignition 0, Ignition 1, Crank and Accessory circuits from the ignition switch. The BCM uses the voltage state, either B+ or 0, and the sequence of state changes to determine the power mode called for by the ignition switch. Refer to the table in Body Control System Description and Operation .

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
    • The BCM detects an improper voltage on one of the ignition switch circuits.
    • One of the ignition switch circuits may be shorted to either B+ or ground.
    • The sequence of the change of the circuit may be incorrect for the expected power mode.

Action Taken When the DTC Sets
    • The BCM stores the DTC 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
    • The current DTC will clear when the BCM detects a sequence of ignition switch inputs that match the expected power mode.
    • A history DTC will clear after 100 ignition cycles with no repeated malfunction.

Step

Action

Yes

No

Schematic Reference: Body Control System Schematics

1

Perform the diagnostic system check for the system that exhibits symptoms. Refer to Control Module References .

Did you perform the Diagnostic System Check?

Go to Step 2

Go to Control Module References

2
  1. Install a scan tool.
  2. Turn OFF the ignition.
  3. With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
    4. • Ignition 0
    • Ignition 1
    • Crank
    • Accessory

Does the scan tool indicate that all inputs are Not Present?

Go to Step 3

Go to Step 8

3
  1. Turn ignition to ACCESSORY.
  2. With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
    3. • Ignition 0
    • Ignition 1
    • Crank
    • Accessory

Does the scan tool indicate that the Accessory input is Present?

Go to Step 4

Go to Step 10

4
  1. Turn ignition to UNLOCK.
  2. With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
    3. • Ignition 0
    • Ignition 1
    • Crank
    • Accessory

Does the scan tool indicate that the Ignition 0 input is Present?

Go to Step 5

Go to Step 10

5
  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
    3. • Ignition 0
    • Ignition 1
    • Crank
    • Accessory

Does the scan tool indicate that the Ignition 0, Ignition 1 and Accessory inputs are Present?

Go to Step 6

Go to Step 10

6

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

  1. Turn ignition to CRANK/START.
  2. With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
    3. • Ignition 0
    • Ignition 1
    • Crank
    • Accessory

Does the scan tool indicate that the Ignition 0, Ignition 1 and Crank inputs are Present?

Go to Step 7

Go to Step 10

7

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

Go to Step 8

Go to Step 13

8
  1. Disconnect the ignition switch harness connectors.
  2. With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
    3. • Ignition 0
    • Ignition 1
    • Crank
    • Accessory

Does the scan tool indicate that any of the Ignition 0, Ignition 1 or Crank inputs are Present?

Go to Step 9

Go to Step 11

9
  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 16

Go to Step 13

10
  1. Disconnect the ignition switch connectors.
  2. Install a 3A fused jumper between the suspect circuits and an ignition switch B+ supply.
  3. With a scan tool, monitor the suspect circuits in Body Control Module, Data Display, Inputs:

Does the scan tool indicate that the suspect circuits are now Present?

Go to Step 11

Go to Step 12

11

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 16

Go to Step 14

12
  1. Disconnect the BCM harness connectors.
  2. Test the suspect ignition switch input circuit(s) 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 16

Go to Step 13

13

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 16

Go to Step 15

14

Replace the ignition switch. Refer to Ignition Switch Replacement - On Vehicle in Steering Wheel and Column.

Did you complete the replacement?

Go to Step 16

--

15

Important: Perform the set up procedure for the BCM. Refer to Body Control Module (BCM) Programming/RPO Configuration .

Replace the BCM. Refer to Body Control Module Replacement .

Did you complete the replacement?

Go to Step 16

--

16
  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