GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Firebird 🢒 Body and Accessories 🢒 Body Control System 🢒 DTC 12 Diagnostic System Check

Circuit Description

Voltage is applied at all times from the POWER ACCY Fuse 7 through circuit 640 to the SECURITY indicator lamp on the instrument cluster.

Ground is applied by the body control module (BCM) through circuit 728 to the SECURITY indicator lamp when the ignition switch is in the RUN or BULB TEST position.

When the ignition switch is turned to the RUN or BULB TEST position, the SECURITY indicator lamp illuminates for approximately 5 seconds in order to verify the circuit operation.

The BCM also uses the SECURITY indicator lamp in order to display the DTC flash codes by grounding CKT 728.

Conditions for Setting the DTC

DTC 12 is always set and displayed when the body control module (BCM) is in the diagnostic mode. DTC 12 indicates that the diagnostic function is in progress. If DTC 12 does not display when the BCM is in the diagnostic mode, refer to the following diagnostic chart.

Test Description

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

  1. This step tests the SECURITY indicator lamp operation at the BULB TEST.

    2.

  2. This step tests the BCM operation in the diagnostic mode.

    3.

  3. This step tests the BCM output to the retained accessory power (RAP) components.

    4.

  4. This step tests circuit 75 for a short to ground.

    5.

  5. This step tests the BCM operation in the diagnostic mode after the repair to circuit 75.

    6.

  6. If the SECURITY indicator lamp does not illuminate, this step determines if the fault is in the BCM or the SECURITY indicator circuit.

    7.

  7. This step tests for a poor connection at the BCM.

    8.

  8. This step tests for an open in circuit 640.

    9.

  9. This step tests for an open in circuit 728.

Step

Action

Value(s)

Yes

No

1

Turn the ignition switch to the RUN position.

Does the security indicator illuminate during BULB TEST?

--

Go to Step 2

Go to Step 3

2

Attempt to enter the body control module (BCM) diagnostic mode. Refer to Diagnostic Trouble Code (DTC) Displaying .

Does the security indicator flash DTCs?

--

System OK

Go to Step 3

3
  1. Turn the ignition switch to the RUN position.
  2. Attempt to operate the power windows.

Do the power windows work?

--

Go to Step 7

Go to Step 4

4
  1. Disconnect the BCM connector C2.
  2. Connect a test lamp from connector C2 terminal C to ground.

Does the test lamp light?

--

Go to Step 5

Go to Step 6

5
  1. Repair the short to ground in circuit 75.
  2. Attempt to enter the body control module (BCM) diagnostic mode. Refer to Diagnostic Trouble Code (DTC) Displaying .

Does the security indicator flash DTCs?

--

System OK

Go to Step 6

6

Replace the BCM. Refer to Body Control Module Replacement .

Is the repair complete?

--

System OK

--

7
  1. Turn the ignition switch to the OFF position.
  2. Disconnect the BCM connector C3.
  3. Connect a fused jumper from BCM connector C3 terminal C12 to ground.

Does the security indicator illuminate?

--

Go to Step 8

Go to Step 9

8
  1. Test for a poor connection at BCM connector C3 terminal C12.
  2. If OK, replace the BCM. Refer to Body Control Module Replacement .

Is the repair complete?

--

System OK

--

9
  1. Disconnect the instrument cluster connector.
  2. Connect a test lamp from the instrument cluster connector terminal A13 to ground.

Does the test lamp light?

--

Go to Step 10

Go to Step 11

10
  1. Test for an open or poor connection in circuit 728, between the BCM and the instrument cluster.
  2. If OK, replace the instrument cluster.

    3. Refer to Instrument Cluster Replacement .

Is the repair complete?

--

System OK

--

11

Repair the open in circuit 640, between the instrument cluster and S211.

Is the repair complete?

--

System OK

--