GM Service Manual Online
For 1990-2009 cars only

The instrument cluster uses information from other systems in order to deliver information to the driver. Review the general information on the following items before further diagnosis:

    • How the instrument cluster computer system operates
    • How each system interacts with the instrument cluster

This step may prevent the following conditions from occurring:

    • Lost diagnosis time
    • Future misdiagnosis
    • Unnecessary parts replacement

Use a scan tool in order to diagnose the instrument cluster when referred to the instrument cluster in diagnostic procedures. In addition to displaying Diagnostic Trouble Codes (DTCs), the scan tool display may display the following information:

    • The input status
    • The data values used

The scan tool may also cycle many of the following components both on and off.

    • The indicators
    • The gauges

Any of these features may be selected using the scan tool.

Become very familiar with the following instrument cluster information:

    • The capabilities
    • The diagnostic features

The self-diagnostic features are referenced in the DTC tables. These features are very useful in diagnosing non-DTC setting malfunctions as well. Not all circuits that feed information to the instrument cluster will set a code if the fault exists within that circuit. The following circuits will not set a trouble code:

    • The windshield washer solvent level switch input
    • The engine coolant level indicator module switch inputs

The diagnostic tables concerning these circuits are still included within this cell in order to help locate the concerns. Perform the Instrument Cluster Diagnostic System Check, these tables will assist in diagnosis.

Replace the instrument cluster only if the diagnostic procedures specifically direct you to do so. The instrument cluster does not automatically need to be replaced when a short is found in the wiring. Repair the wiring first. Inspect the system for further concerns. Most system malfunctions are traceable to one of the following conditions:

    • Faulty wiring
    • Faulty connectors
    • Faulty components

The instrument cluster is very reliable. The instrument cluster is usually not the cause of a system malfunction. Replacing the instrument cluster before a complete diagnosis will usually result in a recurrence of the original complaint.

Display Input Status

The scan tool also displays the instrument cluster status. Select the instrument cluster status display in order to display the data. Determine if the switched inputs may be properly interpreted. The display also indicates if the input has changed states. For example, when the engine coolant level is OK, the scan tool displays the input status of the engine coolant level switch as INACTIVE. When the engine coolant level is low, the scan tool reads ACTIVE. Use this kind of information when diagnosing a malfunction associated with one of the following conditions:

    • A particular instrument cluster input
    • An input that is shared using another system

Cycle Indicators and Gauges

Use a scan tool in order to cycle the following instrument cluster components:

    • The indicators
    • The gauges

This feature may be used in order to determine if the instrument cluster is able to cycle the indicator or gauge regardless of the condition following components:

    • The inputs
    • Any specific program instructions

Once a test is selected, the scan tool will command the instrument cluster in order to energize the selected indicator or gauge. The displayed information represents only what the instrument cluster commands. The displayed information does not display what action has actually taken place. Inspect the instrument cluster for the ability in order to control each of the selected indicator and gauge functions.

Intermittents and Poor Connections

Intermittent failures in electronic systems may be very difficult to detect and accurately diagnose. The instrument panel cluster tests for different malfunctions under different vehicle conditions. For this reason, a thorough test drive is often needed 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:

    • Wires
    • Connections

When you suspect an intermittent condition, inspect the suspected circuits for the following conditions:

    • 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

The history DTCs indicate that the instrument cluster has previously detected a malfunction. The reason may be one of the following conditions:

    • The malfunction is intermittent.
    • The system for which the DTC is set for is not currently being operated.

Use a scan tool in order to try clearing the DTCs and manually operating the system that the DTC applies to, if the following conditions occur:

    • The instrument cluster displays history DTCs.
    • The malfunction cannot be found easily.

Read the Diagnostic Aids and Conditions for Setting the DTC in each DTC table for more specific information.

History DTCs help in diagnosing the intermittent fault conditions but do not necessarily indicate a faulty instrument cluster. Most system complaints are linked to the following conditions:

    • Faulty wiring
    • Faulty connectors
    • A component

Perform a thorough inspection of all the related wiring and connectors pertaining to the history DTC that is stored.

The following conditions may result in an intermittent instrument cluster operation using 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

DTCs Current and History

The instrument cluster stores the DTCs as one of the following codes:

    • A current
    • A history

If the instrument cluster detects a system malfunction, the instrument cluster will only store a DTC that corresponds to that particular malfunction. Some DTCs may remain current until the first ignition cycle if the following conditions occur:

    • A current DTC is stored.
    • The fault is no longer present.

Other DTCs will go history under the following conditions:

    • The fault is no longer present.
    • The fault does not require an ignition cycle.

The history DTCs are intermittent malfunctions. These must be diagnosed differently than the current DTCs. Refer to Intermittents and Poor Connections above.