GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 Regal 🢒 Body and Accessories 🢒 Keyless Entry 🢒 Diagnostic System Check - Body Control System

Object Number: 385141 Size: MF

System Description

The Body Control Module (BCM) diagnostic system check is an organized approach to identify problems associated with the BCM. The BCM diagnostic system check must be the starting point for any BCM-related complaint. The BCM diagnostic system check will direct you to the next logical step in diagnosing the complaint. The BCM is a very reliable component and it is not likely the cause of the malfunction. Most BCM system malfunctions are linked to faulty wiring, connectors, and occasionally to other vehicle components. Understanding the BCM and using the diagnostic tables correctly will reduce diagnostic time and prevent unnecessary parts replacement.

Diagnostic Aids
    • Use a J 35616-A when probing or checking electrical connector terminals. The J 35616-A prevents terminal damage, plus checks for proper terminal contact tension.
    •  If the BCM malfunction is intermittent, refer to Intermittents and Poor Connections for more information.
    • Exit all scan tool tests before cycling the ignition switch to off, unless indicated by the scan tool. Follow the scan tool user's manual. Failure to follow these instructions may set DTCs, cause vehicle system malfunctions, set false DTCs, or cause scan tool malfunctions.
    • DTC P1626 will set in the Powertrain Control Module (PCM) when the ignition switch is on with the Body Control Module (BCM) disconnected. When BCM diagnostics and repairs are completed, refer to Engine Controls for additional information on PCM related DTCs.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. Determines whether the Class 2 serial data link has a circuit malfunction or the BCM is not communicating with the scan tool.

    2.

  2. Tests for a short to ground in circuit 2340.

    3.

  3. Tests for an open in circuit 2340.

    4.

  4. Tests for an open in circuit 1550.

    5.

  5. Tests for an open in circuit 1037.

    6.

  6. Tests for a faulty BCM.

    7.

  7. Tests for BCM current DTCs stored in memory.

    8.

  8. Tests for BCM history DTCs stored in memory.

    9.

  9. Tests for an intermittent BCM system malfunction.

Step

Action

Value(s)

Yes

No

1
  1. Turn the ignition switch off.
  2. Connect a scan tool to the Data Link Connector (DLC).
  3. Turn the ignition switch on.
  4. Using scan tool, attempt to establish communication with the Body Control Module (BCM). Refer to Scan Tool Diagnostics for more information.

Does the scan tool establish communication with the BCM?

--

Go to Step 15

Go to Step 2

2

Using scan tool, attempt to establish communications with these vehicle systems:

    • Powertrain Control Module (PCM)
    • Instrument Cluster
    • Electronic Brake Traction Control Module (EBTCM)
    • SDM and HVAC (w/CJ2)

Does the scan tool communicate with the vehicle systems listed above?

--

Go to Step 3

Go to Step 9

3

Test the BCM-PWR fuse.

Is the BCM-PWR fuse open?

--

Go to Step 4

Go to Step 5

4

  1. Replace the BCM-PWR fuse.
  2. Turn the ignition switch off.
  3. Turn the ignition switch on.
  4. Test the BCM-PWR fuse again.

Is the BCM-PWR fuse open again ?

--

Go to Step 10

Go to Step 5

5

  1. Turn the ignition switch off.
  2. Disconnect the BCM connector C3.
  3. Using a test light, connect between the BCM harness connector C3 terminal B and ground.

Is the test light on?

--

Go to Step 6

Go to Step 11

6

Using a test light, connect between the BCM harness connector C3 terminals B and D.

Is the test light on?

--

Go to Step 7

Go to Step 12

7

  1. Disconnect the BCM connector C2.
  2. Disconnect the scan tool from the DLC.
  3. Using a DMM, measure the resistance between the BCM harness connector C2 terminal B5 and the DLC terminal 2.

Is the resistance within the specified range?

Less than 2ohms

Go to Step 8

Go to Step 13

8

  1. Reinstall connectors/components removed.
  2. Turn the ignition switch on.
  3. Using scan tool, attempt to establish communication with the BCM.

Does the scan tool establish communication with the BCM?

--

Go to Step 15

Go to Step 14

9

The scan tool is unable to establish communication with vehicle systems because of a Class 2 serial data link circuit malfunction. Refer to Diagnostic System Check - Data Link Communications in Wiring Systems for the diagnosis and repair of the Class 2 serial data link.

Is the action complete?

--

Go to Step 1

--

10

Repair short to ground in circuit 2340.

Is the repair complete?

--

Go to Step 1

--

11

Repair poor connection or open in circuit 2340.

Is the repair complete?

--

Go to Step 1

--

12

Repair poor connection or open in circuit 1550.

Is the repair complete?

--

Go to Step 1

--

13

Repair poor connection or open in circuit 1037.

Is the repair complete?

--

Go to Step 1

--

14
  1. Replace the BCM. Refer to Body Control Module Replacement for more information.
  2. After replacing the BCM, perform the Setup New BCM procedure. Refer to BCM Programming/RPO Configuration for more information.

Is the repair complete?

--

Go to Step 1

--

15

Using scan tool, Test for BCM current DTCs. Refer to Diagnostic Trouble Code (DTC) Displaying for more information.

Are any BCM current DTCs present?

--

Go to Step 16

Go to Step 19

16

  1. Write down BCM current DTC(s).
  2. Using scan tool, Test for DTC history DTC(s). Refer to Diagnostic Trouble Code (DTC) Displaying for more information.

Are any BCM history DTCs present?

--

Go to Step 17

Go to Step 18

17
  1. Write down BCM history DTC(s).
  2. For each BCM current DTC, perform corresponding diagnostic table. Refer to Diagnostic Trouble Code (DTC) List/Type for more information. When dealing with several current DTCs, start with DTC with the lowest number, then proceed to the next DTC with a higher number until all current DTCs are diagnosed and repaired.
  3. For each BCM history DTC, go to corresponding diagnostic table and read the circuit description. Refer to Diagnostic Trouble Code (DTC) List/Type for more information. When dealing with several history DTCs, start with DTC with the lowest number, then proceed to the next DTC with a higher number until all history DTCs are reviewed.
  4. History DTCs deal with intermittent malfunction that may not be present at this time. Attempt to repeat the malfunction by following the suggestions listed in diagnostic aids.
  5. Each diagnostic table gives information on the criteria that the BCM uses to set the DTC. This information will help you locating and fixing the condition that caused the intermittent malfunction.

Is the action complete?

--

Go to Step 1

--

18

For each BCM current DTC, perform corresponding diagnostic table. Refer to Diagnostic Trouble Code (DTC) List/Type for more information. When dealing with several current DTCs, start with DTC with the lowest number, then proceed to the next DTC with a higher number until all current DTCs are diagnosed and repaired.

Is the action complete?

--

Go to Step 1

--

19

Using scan tool, test for BCM history DTC(s). Refer to Diagnostic Trouble Code (DTC) Displaying for more information.

Are any BCM history DTCs present?

--

Go to Step 20

--

20
  1. Write down BCM history DTC(s).
  2. For each BCM history DTC, go to corresponding diagnostic table and read the circuit description. Refer to Diagnostic Trouble Code (DTC) List/Type for more information. When dealing with several history DTCs, start with DTC with the lowest number, then proceed to the next DTC with a higher number until all history DTCs are reviewed.
  3. History DTCs deal with intermittent malfunction that may not be present at this time. Attempt to repeat the malfunction by following the suggestions listed in diagnostic aids.
  4. Each diagnostic table gives information on the criteria that the BCM uses to set the DTC. This information will help you locating and fixing the condition that caused the intermittent malfunction.

Is the action complete?

--

Go to Step 1

--