GM Service Manual Online
For 1990-2009 cars only

The instrument panel cluster (IPC) scan tool data display values and definition information can assist in diagnosing conditions that are related to the IPC. The information is especially useful when no diagnostic trouble codes (DTCs) are stored in memory. Compare the vehicles scan tool data with the data display values from a known good vehicle in the Scan Tool Data Display Table. When the data from the vehicle differs from the typical data display value, the data definition information will help to understand the nature of the difference and the source of the problem.

Data

Vehicle Speed

Range: 0 MPH -- 120 MPH (0 KM -- 193 KM)

This data is the cluster is measurement of the vehicle speed. This data is provided by a discrete input from the VCM/PCM.

Engine Speed

Range: 0 RPM -- 7,000 RPM

This data is the cluster is measurement of the engine speed in revolutions per minute (RPM). This data is provided by a discrete input from the VCM/PCM.

Monitored Coolant Temperature

Range: -40-419°F (-40-215°C)

This data is the cluster is measurement of the engine coolant temperature. The data is provided by the VCM/PCM on the Class 2 serial data line. If a Class 2 communication failure occurs, this data will be -40°F (-40°C).

Displayed Coolant Temperature

Range: 32-127°C (90°F -- 260°F)

This data is the coolant temperature that the IPC is attempting to display on the coolant temperature gage. The displayed coolant temperature may differ from the monitored coolant temperature for a period of time due to filtering. The monitored coolant temperature may also differ when the coolant temperature is not in the range of 32-127°C (90° F -- 260° F) because the display has limited values. If a Class 2 communication failure occurs the data will be at the minimum value of 32°C (90°F).

Monitored Fuel Level

Range: 0-100 percent

This data is the cluster's measurement of the fuel tank level. The data is provided by the VCM/PCM on the Class 2 serial data line. If a Class 2 communication failure occurs, this data will be 0.

Displayed Fuel Level

Range: 0-100 percent

This data is the fuel level that the IPC is attempting to display on the fuel gage. The displayed fuel level may differ from the monitored fuel level for a period of time due to filtering. If a Class 2 communication failure occurs, this data will be 0.

Odometer Display

Range: 0-999,999 (km or miles)

This data refers to the displayed odometer distance on the odometer display.

Displayed Trip Odometer

Range: 0-9,999 (km or miles)

This data refers to the displayed trip odometer distance that is displayed on the trip odometer display.

Battery Voltage

Range: 9.0-9.0 v

This data refers to the battery system voltage. The voltage is measured by the IPC.

Inputs

PRNDL State

Range: Park/ Reverse/ Neutral/ Drive/ Third/ Second/ First/ Invalid

This data input refers to the PRNDL position data that is communicated to the cluster over the Class 2 serial data line by the PCM/VCM . The value of this parameter corresponds to the gear selected on the PRNDL display. The value of this parameter will be INVALID under the following conditions:

    • The data from the PCM/VCM is INVALID.
    • The data from the PCM/VCM is PARK but the cluster does not see ground on the park switch input (pin A12).
    • The data from the PCM/VCM is not PARK but the cluster sees ground on the park switch input (pin A12).
    • A Class 2 communication failure has occurred.

When the value of the parameter in INVALID, no gear will be shown as selected on the PRNDL display.

Dimming

Range: Active/Inactive

This data refers to the dimming availability feature of the PRNDL and the odometer/trip odometer vacuum florescent displays.

ACTIVE is displayed when the park lamps are ON.

When ACTIVE is displayed, you can use the thumbwheel dimming switch in order to dim the following displays:

    • The PRNDL
    • The odometer/trip odometer vacuum florescent

INACTIVE is displayed when the Park Lamps are OFF.

When INACTIVE is displayed, you cannot dim the following displays:

    • The PRNDL
    • The odometer/trip odometer vacuum florescent

Park Switch

Range: Open / Closed

This data input refer to the state of the gear shift PARK position switch.

OPEN is displayed when the gear shift is not in PARK.

CLOSED is displayed when the following conditions exist:

    • The gear shift is in the PARK position
    • The gear shift lever is at the normal rest position.

Trip Reset Switch

Range: ON/ OFF

This data refers to the position of the Trip Odometer Reset Switch.

ACTIVE is displayed when the Trip Reset Switch is pushed in.

INACTIVE is displayed when the Trip Reset Switch is in the normal position.

Outputs

Check Gauges Lamp

Range: ON/ OFF

This output refers to the commanded state of the CHECK GAUGES lamp illumination by the IPC module.

ON is displayed when the IPC module is commanding the CHECK GAUGES lamp to illuminate.

The IPC module commands the lamp to illuminate when one of the following conditions exist:

    • The lamp receives a high engine coolant temperature (less than 120°C or 248°F) Class 2 message from the VCM/PCM.
    • The lamp receives a low oil pressure signal (less than 5ohms) from the oil pressure sender. The bulb check is occurring when the engine is running.
    • The bulb check period lasts for 3 seconds after the ignition switch is first turned to RUN.

OFF is displayed when the IPC module is not commanding the CHECK GAUGES lamp to be illuminated.

Low Fuel Lamp

Range: ON/ OFF

This output refers to the commanded state of the LOW FUEL lamp illumination by the IPC module.

ON is displayed when the IPC module is commanding the LOW FUEL lamp to be illuminated.

OFF is displayed when the IPC module is not commanding the LOW FUEL lamp to be illuminated.

The IPC will command the LOW FUEL lamp to be illuminated under the following conditions:

    • The lamp receives a Class 2 (percent of monitored fuel level) message of less than 19.2 percent from the VCM/PCM. Once the lamp is on, the monitored fuel level must rise above 23 percent in order to turn off the lamp.
    • During the bulb check period after the ignition switch is first turned to the RUN position.
    • A Class 2 communication failure has occurred.

Service 4WD

Range: ON/ OFF

This output refers to the commanded state of the SERVICE 4WD lamp illumination by the IPC module.

ON is displayed when the IPC module commands the SERVICE 4WD lamp to be illuminated when a Class 2 message from the automatic transfer case (ATC) module is received.

OFF is displayed when the IPC module is not commanding the SERVICE 4WD lamp to be illuminated.

Overspeed Lamp

Range: ON/ OFF

This output refers to the OVERSPEED lamp illumination by the IPC module.

ON is displayed when the IPC module commands the OVERSPEED lamp to flash when a Class 2 message is received from the VCM/PCM.

OFF is displayed when the IPC module does not command the OVERSPEED lamp to be illuminated.

ABS Lamp

Range: ON/ OFF

This output refers to the ABS lamp illumination by the IPC module.

ON is displayed when the IPC module commands the ABS lamp to be illuminated.

OFF is displayed when the IPC module does not command the ABS lamp to be illuminated.

The IPC will command the ABS lamp to be illuminated under the following conditions:

    • A Class 2 message is received from the electronic brake control module (EBCM). A Class 2 message indicates that there is a malfunction in the ABS system.
    • During the bulb check period, for 3  seconds after the ignition switch is first turned to the RUN position.
    • A Class 2 communication failure occurs.

Brake Lamp

Range: ON/ OFF

This output refers to the commanded state of the BRAKE lamp illumination by the IPC module.

ON is displayed when the IPC module commands the BRAKE lamp to be illuminated.

The BRAKE lamp illuminates under the following conditions:

    • A Class 2 message is received from the body control module (BCM) indicating the parking brake is set.
    • A Class 2 message is received from the electronic brake control module (EBCM). A Class 2 message indicates a condition with the base brake system (non-ABS portion).
    • During the bulb check period, for 3 seconds after the ignition switch is first turned to the RUN position.

OFF is displayed when the IPC module does not command the BRAKE lamp to be illuminated.

Fasten Seat Belts

Range: ON/ OFF

This output refers to the commanded state of the FASTEN SEAT BELTS lamp illumination by the IPC module.

ON is displayed under the following conditions:

    •  When the IPC module commands the FASTEN SEAT BELTS lamp to be illuminated for 20 seconds. The illumination is followed by 55  seconds of flashing, a Class 2 message received from the body control module (BCM) indicating the driver seat belt is not fastened.
    • During the bulb check period for 3  seconds after the ignition switch is first turned to the RUN position, providing the driver' buckle is fastened.

OFF is displayed when the IPC module is not commanding the FASTEN SEAT BELTS lamp to be illuminated.

Security Lamp

Range ON/ OFF

This output refers to the commanded state of the SECURITY lamp illumination by the IPC module.

ON is displayed when the IPC module commands the SECURITY lamp to be illuminated.

The IPC will command the SECURITY lamp to be illuminated under the following conditions:

    • A Class 2 message from the body control module is received.
    • During the bulb check period, for 3 seconds after the ignition switch is first turned to the RUN position.
    • A Class 2 communication failure occurs.

OFF is displayed when the IPC does not command the SECURITY lamp to be illuminated.

Rear Gate/ Door

Range : OPEN/ CLOSED

This output refers to the commanded state of the REAR GATE/ DOOR lamp illumination by the IPC module.

ON is displayed when the IPC module is commanding the REAR GATE/ DOOR lamp to be illuminated when a Class 2 message from the body control module (BCM) is received.

OFF is displayed when the IPC module does not command the REAR GATE/ DOOR lamp to be illuminated.

Upshift Lamp

Range ON/OFF (Manual Transmission Vehicle Only)

This output refers to the commanded state of the UPSHIFT lamp illumination by the IPC module.

ON is displayed when the IPC module commands the UPSHIFT lamp to be illuminated when a Class 2 message is received from the PCM/VCM.

OFF is displayed when the IPC module does not command the UPSHIFT lamp to be illuminated.

High Beam Lamp

Range: ON/ OFF

This output refers to the commanded state of the high beam lamp illumination by the IPC module.

ON is displayed when the IPC module commands the high beam lamp to be illuminated when a Class 2 message from the body control module (BCM) is received.

OFF is displayed when the IPC module does not command the UPSHIFT lamp to be illuminated.

Battery

Range: ON/ OFF

This output refers to the commanded state of the BATTERY (voltage) lamp illumination by the IPC module.

ON is displayed when the IPC module commands the BATTERY lamp to be illuminated.

OFF is displayed when the IPC module does not command the BATTERY lamp to be illuminated.

The IPC will command the BATTERY lamp to be illuminated under the following conditions:

    • A Class 2 message from the PCM/VCM indicating a charging system condition.
    • The ignition switch is turned to UNLOCK or RUN without the engine running.
    • A Class 2 communication failure occurs.