GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The instrument cluster receives voltage inputs from 3 ignition signals. The instrument cluster receives voltage from the IGN 01 fuse when the ignition switch is in the off, accessory, on or start positions. The instrument cluster receives voltage from the CLUSTER fuse when the ignition switch is in the on and start positions. The instrument cluster receives voltage from the CRANK SIGNAL fuse when the ignition switch is in the START position. If the instrument cluster does not receive any of the following voltage input combinations, a malfunction is present and this DTC sets:

    • If circuit 39 is active and circuit 1500 is inactive
    • If circuit 806 is active and circuit 1500 is inactive
    • If circuit 806 is active and circuit 39 is inactive

Conditions for Setting the DTC

    • The instrument cluster does not detect voltage from circuit 1500 when the ignition switch is in the accessory, on or start positions, but the instrument cluster detects voltage in circuit 39 when the ignition switch is in the on or start positions.
    • The instrument cluster detects voltage in circuit 806 when the ignition switch is in the start position, but the instrument cluster does not detect voltage in circuit 1500 when the ignition switch is in the accessory, on or start positions.
    • The instrument cluster detects voltage in circuit 806 when the ignition switch is in the start position, but the instrument cluster does not detect voltage in circuit 39 when the ignition switch is in the on or start positions.
    • All conditions must be present for more than 0.3 seconds.

Action Taken When the DTC Sets

    • The instrument cluster stores DTC B0608 in memory.
    • The SERVICE VEHICLE SOON indicator turns on.

Conditions for Clearing the DTC

    • Under all fault conditions the ignition switch must be cycled from on to off, back to on before this DTC can change from current to history.
    • The instrument cluster no longer detects an open or short to B+ in circuit 39, circuit 806, and circuit 1500.
    • A history DTC will clear after 100 drive cycles if the condition for this DTC is no longer present.
    • Use a scan tool.

Diagnostic Aids

The following conditions may cause an intermittent malfunction to occur:

   • 

An intermittent open or short to voltage in circuit 39, circuit 806, or circuit 1500

   • 

Poor connections at the instrument cluster or fuse block

   • 

The instrument cluster is always detecting B+ from one or more of these 3 inputs.

   • 

The instrument cluster is never recognizing B+ from circuit 39, circuit 806, or circuit 1500.

Test Description

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

  1. Always perform the instrument cluster diagnostic system check before attempting to diagnose DTC B0608.

  2. This test will determine if there is a short to B+ in circuit 39.

  3. This test checks for an open in circuit 39.

  4. This test will determine if there is a short to B+ in circuit 806.

  5. This test checks for an open in circuit 806.

  6. This test will determine if there is a short to B+ in circuit 1500.

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

Step

Action

Value(s)

Yes

No

1

Was the Instrument Cluster Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

2

  1. Turn the ignition switch off.
  2. Disconnect the instrument cluster connector.
  3. Turn the ignition switch to the accessory position.
  4. Using a test light and a J 35616A kit, frontprobe between the instrument cluster harness connector terminal B12 and ground.

Does the test light stay off?

--

Go to Step 4

Go to Step 3

3

Repair a short to B+ in circuit 39.

Is the repair complete?

--

Go to Step 15

--

4

  1. Leave the test light connected at the same location.
  2. Turn the ignition switch on.

Is the test light on?

--

Go to Step 5

Go to Step 6

5

  1. Turn the ignition switch off.
  2. Using a test light and a J 35616A kit, frontprobe between the instrument cluster harness connector terminal A3 and ground.
  3. While observing the test light, turn the ignition switch from off to accessory, and from accessory to on.

Does the test light stay off?

--

Go to Step 8

Go to Step 7

6

Repair a poor connection or an open in circuit 39 between the instrument cluster harness connector terminal B12 and the fuse block terminal D6.

Is the repair complete?

--

Go to Step 15

--

7

Repair a short to B+ in circuit 806.

Is the repair complete?

--

Go to Step 15

--

8

  1. Leave the test light connected at the same location.
  2. Turn the ignition switch to the start position.

Upon turning the ignition switch to the start position, did the test light turn on?

--

Go to Step 9

Go to Step 10

9

  1. Turn the ignition switch off.
  2. Using a test light and a J 35616A kit, frontprobe between the instrument cluster harness connector terminal A2 and ground.

Does the test light stay off?

--

Go to Step 11

Go to Step 12

10

Repair a poor connection or an open in circuit 806 between the instrument cluster harness connector terminal A6 and the fuse block terminal A4.

Is the repair complete?

--

Go to Step 15

--

11

  1. Leave the test light connected at the same location.
  2. While observing the test light, turn the ignition switch from off to accessory, from accessory to on, and from on to the start position.

Did the test light turn on when the ignition switch was in the accessory, on and start positions?

--

Go to Step 13

Go to Step 14

12

Repair a short to B+ in circuit 1500.

Is the repair complete?

--

Go to Step 15

--

13

Replace the instrument cluster. Refer to Instrument Cluster Replacement .

Is the repair complete?

--

Go to Step 15

--

14

Repair a poor connection or an open in circuit 1500.

Is the repair complete?

--

Go to Step 15

--

15

  1. Turn the ignition switch off.
  2. Reconnect or install any connectors or components that were disconnected or removed.
  3. Clear the DTCs in the instrument cluster. Refer to Clearing DTCs .
  4. Check for DTCs in the instrument cluster. Refer to Diagnostic Trouble Code (DTC) Displaying .

Are there any DTCs stored in the instrument cluster?

--

Go to Diagnostic Trouble Code (DTC) List/Type

System OK