GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The Instrument Cluster Diagnostic System Check is an organized approach in order to identify the problems associated with the instrument cluster. Ensure that this inspection is the starting point for any instrument cluster complaint. This point may direct you to the next logical step in diagnosing the complaint. The instrument cluster is a very reliable component. The instrument cluster is not likely the cause of the malfunction. Most system complaints are due to the following conditions:

    • Faulty wiring
    • Faulty connectors
    • The components

Understanding the computer system and the correct use of the tables may ensure the following conditions:

    • Reduced diagnostic time.
    • Unnecessary parts replacement.

Diagnostic Aids

    • The following conditions may result in an intermittent operation of the instrument cluster with no DTC stored:
       - Any condition which results in the interruption of power to the instrument cluster.
       - The battery or ignition voltage out of range (below 9.0 V or above 16.0 V).
       - A loose or damaged ground.
       - An open or short on the serial data line.
    • An intermittent failure in the electronic system may be very difficult to detect and accurately diagnose. The instrument cluster tests for different malfunctions under different vehicle conditions. For this reason, you need to perform a thorough test drive in order to repeat a fault condition. If the system malfunction is not repeated during the drive test, a good description of the complaint may be useful in locating an intermittent fault condition. The following faulty components cause most intermittent problems:
       - Poor mating of the connector halves.
       - Backed out terminals.
       - Improperly formed or damaged terminals.
       - Wire chafing.
       - Poor wire-to-terminal connections.
       - Dirty or corroded terminals.
       - Damage to the connector bodies.
    • Use a J 35616
       - Probing a terminal
       - Inspecting a terminal
       - Use the adapter in order to ensure the following conditions:
   • No damage to the terminal will occur.
   • Indicate whether the contact tension is sufficient.
    • If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving any related wiring and connectors pertaining to the history DTC stored. Refer to Intermittents and Poor Connections Diagnosis .
    • Exit all the Scan Tool tests before cycling the ignition OFF to ON unless the scan tool instructions direct otherwise. Follow the operating instructions unless the scan tool direct instructions otherwise. Follow the operating instructions in the scan tool operators's manual. Failure to follow these instructions may result in the following conditions to occur:
       - Set the DTCs
       - Cause the vehicle system malfunctions
       - Set the false DTCs
       - Cause a Scan Tool malfunction
    • Inspect all the relative fuses (see schematic) for the instrument cluster. If open, inspect the circuits which are fed power by these fuses for a short to ground.
    • Ensure that all the relative grounds (see schematic) are clean and tight.
    • For Instrument Cluster Removal and Replacement procedures, refer to Instrument Cluster Replacement
    • Inspect for a broken (or partially broken) wire inside of the insulation which may cause one of the following conditions:
       - A system malfunction.
       - A system that is GOOD in a continuity/voltage inspection while the system is disconnected.
       - These circuits may be intermittent or recessive when loaded. If possible, ensure that the circuits are inspected by monitoring for a voltage drop using the system operational (under load).
    • Inspect for the proper installation of the aftermarket electronics equipment which may affect the integrity of the other systems. Refer to Checking Aftermarket Accessories .

Test Description

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

  1. This test determines if the communication may be established using the instrument cluster.

  2. This test inspects for stored instrument cluster DTCs.

  3. This test determines whether communication may be established using other systems connected to the same serial data line.

  4. This test inspects for the instrument cluster power circuits.

  5. This test inspects for the instrument cluster ground circuits.

  6. This test determines if an open is present in the serial data line between the instrument cluster and the DLC terminal (CKT 1036 and CKT 1132).

Step

Action

Value(s)

Yes

No

1

  1. Turn the ignition switch to the OFF position.
  2. Install a Scan Tool .
  3. Turn the ignition switch to the RUN position.
  4. Attempt to establish communication with the instrument cluster.

Does the Scan Tool communicate with the instrument cluster?

--

Go to Step 2

Go to Step 3

2

  1. Select the display instrument cluster Diagnostic Trouble Code (DTC) function with the Scan Tool .
  2. Inspect for any instrument cluster DTCs.

Are any DTCs stored?

--

Go to Diagnostic Trouble Code (DTC) List/Type

System OK

3

Attempt to establish communication with the other systems connected to the same serial data line.

Does the Scan Tool communicate with the other systems?

--

Go to Step 4

Go to Data Link Communications System Check in Wiring Systems

4

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the instrument cluster connector.
  3. Turn the ignition switch to the RUN position.
  4. Use a test light in order to backprobe between the following instrument cluster power circuits and ground:
  5. • A2-640
    • B12-39
    • A8-1500

Does the test lamp light for all of the circuits?

--

Go to Step 5

Go to Step 8

5

Use a test light in order to backprobe between B+ and each of the following circuits:

    • A12-1550
    • A1-1750

Does the test lamp light for all of the circuits?

--

Go to Step 6

Go to Step 9

6

  1. Zero the J 39200 digital multimeter (DMM)
  2. Use a J 39200 in order to measure for continuity in CKT 1036 and CKT 1132 between the following terminals:
  3. • Instrument cluster harness connector terminal B2
    • DLC terminal 2

Is there continuity in CKT 1036 and CKT 1132?

--

Go to Step 7

Go to Step 10

7

  1. Replace the instrument cluster. Refer to Instrument Cluster Replacement .
  2. Inspect the system.

Is the repair complete?

--

System OK

--

8

  1. Repair the following conditions in the faulty instrument cluster power circuit:
  2. • A poor connection
    • An open
  3. Clear all of the DTCs from the memory.
  4. Inspect the system.

Is the repair complete?

--

System OK

--

9

  1. Repair the following conditions in the faulty instrument cluster ground circuit:
  2. • A poor connection
    • An open
  3. Clear all of the DTCs from the memory.
  4. Inspect the system.

Is the repair complete?

--

System OK

--

10

  1. Repair the following conditions in CKT 1036 and CKT 1132 between the data link connector terminal 2 and the instrument cluster harness connector terminal B2:
  2. • A poor connection
    • An open
  3. Clear all of the DTCs from memory.
  4. Inspect the system.

Is the repair complete?

--

System OK

Go to Data Link Communications System Check in Wiring Systems