GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 Century (China) (CNG) 🢒 Body and Accessories 🢒 Body Control System 🢒 DTC B0608 BCM Power Moding Error

Object Number: 501866 Size: MF

Circuit Description

The BCM receives three voltage inputs. The BCM receives voltage from the IGN 0 fuse through circuit 1500 at all times except when the ignition switch is off. The BCM receives voltage from the PCM-BCM fuse through circuit 439 when the ignition switch is in the on or start position. The BCM receives voltage from the CRANK SIGNAL fuse through circuit 806 when the ignition switch is in the start position.

Conditions for Setting the DTC

The BCM sets DTC B0608 when detecting any of these conditions for more than 0.3 seconds:

    • Voltage in circuit 439 is high and voltage in circuit 1500 is low.
    • Voltage in circuit 806 is high and voltage in circuit 1500 is low.
    • Voltage in circuit 806 is high and voltage in circuit 439 is low.

Action Taken When the DTC Sets

the BCM stores DTC B0608 in memory.

Conditions for Clearing the DTC
    • The BCM no longer detects an open or short to B+ in circuits 439, 806, or 1500.
    • A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
    • Using a scan tool.

Diagnostic Aids

The following conditions may cause an intermittent malfunction to occur:

    • An intermittent open or short to B+ in circuit 439, 806, or 1500.
    • Poor connections at the BCM, or the fuse block.
    • The BCM is always detecting B+ in circuits 439, 806, or 1500.
    • The BCM is never detecting B+ in circuits 439, 806, and 1500.

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 Powertrain On Board Diagnostic (OBD) System Check

Test Description

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

  1. This step checks for a short to ground in circuit 806.

    2.

  2. This step checks for a short to ground in circuit 1500.

    3.

  3. This step checks for a short to B+ in circuit 1500.

    4.

  4. This step checks for an open in circuit 439.

    5.

  5. This step checks for a short to B+ in circuit 806.

    6.

  6. This step checks for an open in circuit 806.

    7.

  7. This step checks for a short to B+ in circuit 1500.

    8.

  8. This test checks for an open in circuit 1500.

    9.

  9. This test determines whether the malfunction is intermittent or the BCM is faulty.

Step

Action

Value(s)

Yes

No

1

Was the BCM Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - Body Control System

2

Check fuse A3-4.

Is fuse A3-4 open?

--

Go to Step 3

Go to Step 4

3
  1. Turn the ignition switch to the LOCK position.
  2. Replace fuse A3-4.
  3. Turn the ignition switch to the START position momentarily.

    4. NOTE: The engine may start.

  4. Check fuse A3-4 again.

Is fuse A3-4 open again?

--

Go to Step 13

Go to Step 4

4

Check fuse A7-8.

Is fuse A7-8 open?

--

Go to Step 5

Go to Step 6

5
  1. Turn the ignition switch to the LOCK position.
  2. Replace fuse A7-8.
  3. Turn the ignition switch to the RUN position.
  4. Check fuse A7-8 again.

Is the IGN 0 fuse open again?

--

Go to Step 14

Go to Step 6

6

  1. Turn the ignition switch to the LOCK position.
  2. Using a test light, backprobe between the BCM connector C1 terminal C12 and ground.

Does the test light stay off?

--

Go to Step 7

Go to Step 15

7
  1. Leave the test light connected from the previous step.
  2. While observing the test light, turn the ignition switch to the RUN position, then to the START position.

    3. NOTE: The engine may start.

  3. Turn the ignition switch to the LOCK position.

Was the test light on with the ignition switch in the RUN and START position?

--

Go to Step 8

Go to Step 16

8

  1. Using a test lamp, backprobe between the BCM connector C1 terminal C13 and ground.
  2. While observing the test lamp, turn the ignition switch from LOCK to the RUN position.

Did the test lamp stay off when turning the ignition switch from LOCK to RUN?

--

Go to Step 9

Go to Step 17

9

  1. Leave the test lamp connected from the previous step.
  2. Turn the ignition switch to the START position momentarily.

    3. NOTE: The engine may start.

  3. Turn the ignition switch to the LOCK position.

Did the test lamp turn on when turning the ignition switch to START?

--

Go to Step 10

Go to Step 18

10

  1. Make sure the ignition switch is in the LOCK position.
  2. Using a test light, connect by backprobing between the BCM connector C1 terminal C3 and ground.

Does the test lamp stay off?

--

Go to Step 11

Go to Step 19

11

  1. Leave the test light connected from the previous step.
  2. While observing the test lamp. turn the ignition switch to OFF, then to RUN, then to START.

    3. NOTE: The engine may start.

Did the test light turn on with the ignition switch in the OFF, RUN or START position?

--

Go to Step 12

Go to Step 20

12

  1. Turn the ignition switch to the RUN position.
  2. Clear the BCM DTCs. Refer to Clearing DTCs for more information.
  3. Turn the ignition switch to the LOCK position.
  4. Wait 10 seconds.
  5. Turn the ignition switch to the RUN position.
  6. Check for the BCM DTCs. Refer to Diagnostic Trouble Code (DTC) Displaying for more information.

Does DTC B0608 reset as a current DTC?

--

Go to Step 21

Go to Step 22

13
  1. Repair short to ground in circuit 806.
  2. Replace the fuse.

Is the repair complete?

--

Go to Step 23

--

14
  1. Repair short to ground in circuit 1500.
  2. Replace the fuse.

Is the repair complete?

--

Go to Step 23

--

15

Repair short to voltage in circuit 439.

Is the repair complete?

--

Go to Step 23

--

16

Repair poor connection or open in circuit 439.

Is the repair complete

--

Go to Step 23

--

17

Repair short to voltage in circuit 806 or a faulty ignition switch.

Is the repair complete?

--

Go to Step 23

--

18

Repair poor connection or open in circuit 806.

Is the repair complete?

--

Go to Step 23

--

19

Repair short to voltage in circuit 1500 or a faulty ignition switch.

Is the repair complete?

--

Go to Step 23

--

20

Repair poor connection or open in circuit 1500.

Is the repair complete?

--

Go to Step 23

--

21
    • Check the BCM connector C1 terminals C3, C12, and C13 for poor terminal contact.
    • If the connections are OK, then replace the BCM. Refer to Body Control Module Replacement for more information.
    • After replacing the BCM, perform the Setup new BCM procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration for more information.

Is the repair complete?

--

Go to Step 23

--

22

The malfunction is not present at this time. Refer to Diagnostic Aids for additional information regarding this DTC.

Is the action complete?

--

Go to Step 23

--

23
  1. Turn the ignition switch to the LOCK position.
  2. Reinstall connectors/components removed.
  3. Turn the ignition switch to the RUN position.
  4. Clear the BCM DTCs. Refer to Clearing DTCs for more information.
  5. Check for BCM DTCs. Refer to Diagnostic Trouble Code (DTC) Displaying for more information.

Are there any BCM current DTCs set?

--

Go to Diagnostic System Check - Body Control System

System OK