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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1999 🢒 Montana Ext. 🢒 Body and Accessories 🢒 Body Control System 🢒 Diagnostic System Check - Body Control System

System Description

The Body Control Module (BCM) diagnostic system check is an organized method for defining problems that are associated with the BCM. Start with a diagnostic system check when you have a concern. The diagnostic system check will lead to the next logical step in diagnosis.

The BCM is a reliable component and is not often the cause of a malfunction. Most system complaints are caused by the following items:

    • Faulty wiring
    • Faulty connectors
    • Faulty components

If you understand the computer system and use the tables correctly, you will reduce diagnostic time and prevent unnecessary replacement of components.

Diagnostic Aids

The following conditions may cause an intermittent operation of the BCM with no diagnostic trouble codes (DTCs) stored:

    • Any condition that results in the interruption of power to the BCM.
    • Battery voltages that are out of the specified range. The normal battery voltage is 9-16 volts.
    • Loose or damaged grounds.

It may be difficult to detect and accurately diagnose an intermittent failure in the electronic system. The BCM tests for different malfunctions under different vehicle conditions. For this reason, a thorough test drive is often necessary in order to repeat a fault condition. Faulty electrical connections or faulty wiring causes most of the intermittent conditions.

When you suspect an intermittent failure, inspect the system for the following conditions:

    • Incomplete mating of the connector halves
    • Backed out terminals
    • Incorrectly formed terminals
    • Damaged terminals
    • Wire chafing
    • Faulty connections between the terminals and the wires
    • Dirty or corroded terminals
    • Damage to the connector bodies

Use a J 35616 whenever a diagnostic procedure requires probing or testing a terminal. Use of the J 35616 ensures the following:

    • No damage occurs to the terminal.
    • Sufficient contact tension.

DTC P1626 sets in the powertrain control module (PCM) when the following conditions exist:

    • The ignition switch is in the RUN position.
    • The body control module (BCM) is disconnected.

When completing BCM diagnostics and repairs, refer to Engine Controls for additional information on PCM related DTCs.

Test Description

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

  1. This step determines if the BCM identifies its BCM type.

  2. This step determines if the vehicle has the correct BCM type installed.

  3. This step inspects for DTCs that are stored in the BCM memory.

  4. This step inspects for a short to ground in CKT 240.

  5. This step inspects for a short to ground in CKT 1540.

  6. This step inspects for a short to ground in CKT 39.

  7. This step inspects for a short to ground in CKT 43.

  8. This step inspects for an open in CKT 1550.

  9. This step inspects for an open in CKT 240.

  10. This step inspects for an open in CKT 1540.

  11. This step inspects for an open in CKT 39.

  12. This step inspects for a short to B+ in CKT 39.

  13. This step inspects for an open in CKT 43.

  14. This step inspects for a short to B+ in CKT 43

  15. This step inspects for a short to B+ in CKT 1445.

  16. This step inspects for an open in CKT 1445.

Step

Action

Value(s)

Yes

No

1
  1. Remove the BCM PRGRM fuse that is located in the fuse block.
  2. Turn the ignition switch to the LOCK position.
  3. Close all of the doors.
  4. Turn the ignition switch to the ACC position.

    5. The BCM enters the feature customization mode. When the features customization mode is active, the BCM identifies its type by flashing the fasten belts indicator and sounding the chime a number of times equal to the BCM type number.

Does the BCM identify its type number?

--

Go to Step 2

Go to Step 4

2

Refer to Body Control System Circuit Description for details on BCM types.

Does the BCM type match the equipment/option content for the vehicle?

--

Go to Step 3

Go to Step 22

3

Within 1 seconds, turn the ignition switch from the ACC position to the LOCK position, then back to the ACC position.

When the switch is cycled, the BCM enters the diagnostics/programming mode. At this point, the BCM may flash and chime any DTCs that are stored in the memory. DTC numbers range between 1 and 8. Refer to Body Control System Circuit Description for more information about DTCs.

Does the BCM display any DTCs?

--

Go to Step 23

Go to Step 4

4

Inspect the CTSY LAMP fuse.

Is the CTSY LAMP fuse open?

--

Go to Step 5

Go to Step 6

5
  1. Replace the CTSY LAMP fuse.
  2. Test the CTSY LAMP fuse again.

Is the CTSY LAMP fuse open again?

--

Go to Step 24

Go to Step 6

6

Test the PWR LOCK fuse.

Is the PWR LOCK fuse open?

--

Go to Step 7

Go to Step 8

7
  1. Replace the PWR LOCK fuse.
  2. Test the PWR LOCK fuse again.

Is the PWR LOCK fuse open again?

--

Go to Step 25

Go to Step 8

8

Test the IGN 1 fuse.

Is the IGN 1 fuse open?

--

Go to Step 9

Go to Step 10

9
  1. Replace the IGN 1 fuse.
  2. Turn the ignition switch to the RUN position.
  3. Test the IGN 1 fuse again.

Is the IGN 1 fuse open again?

--

Go to Step 26

Go to Step 10

10

Test the MALL/RADIO/DIC fuse.

Is the MALL/RADIO/DIC fuse open?

--

Go to Step 11

Go to Step 12

11
  1. Replace the MALL/RADIO/DIC fuse.
  2. Turn the ignition switch to the RUN position.
  3. Test the MALL/RADIO/DIC fuse again.

Is the MALL/RADIO/DIC fuse open again?

--

Go to Step 27

Go to Step 12

12
  1. Turn the ignition switch to the LOCK position.
  2. Disconnect the BCM connector C1.
  3. Use a test lamp in order to connect between B+ and the BCM harness connector C1 terminal D.

Does the test lamp light?

--

Go to Step 13

Go to Step 28

13

Use a test lamp in order to connect the BCM harness connector C1 terminal G and ground.

Does the test lamp light?

--

Go to Step 14

Go to Step 29

14

Use a test lamp in order to connect between the BCM harness connector C1 terminal H and ground.

Does the test lamp light?

--

Go to Step 15

Go to Step 30

15
  1. Disconnect the BCM connector  2.
  2. Turn the ignition switch to the RUN position.
  3. Use a test lamp in order to connect between the BCM harness connector C2 terminal C13 and ground.

Does the test lamp light?

--

Go to Step 16

Go to Step 31

16
  1. Leave the test lamp connected.
  2. Turn the ignition switch to the LOCK position.

Does the test lamp light?

--

Go to Step 32

Go to Step 17

17
  1. Turn the ignition switch to the RUN position.
  2. Use a test lamp in order to connect between the BCM harness connector C2 terminal D4 and ground.

Does the test lamp light?

--

Go to Step 18

Go to Step 33

18
  1. Leave the test lamp connected.
  2. Turn the ignition switch to the LOCK position.

Does the test lamp light?

--

Go to Step 34

Go to Step 19

19

Use a test lamp in order to connect between the BCM harness connector C2 terminal C9 and ground.

Does the test lamp light?

--

Go to Step 35

Go to Step 20

20
  1. Leave the test lamp connected.
  2. Reinstall the BCM PRGRM fuse.

Does the test lamp light?

--

Go to Step 21

Go to Step 36

21
  1. Turn the ignition switch to the LOCK position.
  2. Reconnect the BCM connectors C1 and C2.
  3. Close all of the doors.
  4. Remove the BCM PRGRM fuse.
  5. Turn the ignition switch to the ACC position.

Does the BCM identify its type number?

--

Go to Step 1

--

22

Replace the BCM with the correct BCM type, according to vehicle equipment content and options. Refer to Body Control Module Replacement

Is the repair complete?

--

Go to Step 1

--

23

Refer to the appropriate DTC table for further diagnosis and repair. Is the repair complete?

--

Go to Step 1

--

24

Repair the short to ground in CKT 240.

Is the repair complete?

--

Go to Step 1

--

25

Repair the short to ground in CKT 1540.

Is the repair complete?

--

Go to Step 1

--

26

Repair the short to ground in CKT 39.

Is the repair complete?

--

Go to Step 1

--

27

Repair the short to ground in CKT 43.

Is the repair complete?

--

Go to Step 1

--

28

Repair the poor connection or the open in CKT 1550.

Is the repair complete?

--

Go to Step 1

--

29

Repair the poor connection or the open in CKT 240.

--

Go to Step 1

--

30

Repair the poor connection or the open in CKT 1540.

Is the repair complete?

--

Go to Step 1

--

31

Repair the poor connection or the open in CKT 39.

Is the repair complete?

--

Go to Step 1

--

32

Repair the short to B+ in CKT 39.

Is the repair complete?

--

Go to Step 1

--

33

Repair the poor connection or the open in CKT 43.

Is the repair complete?

--

Go to Step 1

--

34

Repair the short to B+ in CKT 43.

Is the repair complete?

--

Go to Step 1

--

35

Repair the short to B+ in CKT 1445.

Is the repair complete?

--

Go to Step 1

--

36

Repair the poor connection or the open in CKT 1445.

Is the repair complete?

--

Go to Step 1

--

37
  1. Inspect the BCM connectors for poor terminal contact. Repair the terminals as needed.
  2. If the terminal contact is not poor, replace the BCM. Refer to Body Control Module Replacement

Is the repair complete?

--

Go to Step 1

--

38

Were you sent here from another diagnostic table?

--

Go to the appropriate diagnostic table.

System OK