GM Service Manual Online
For 1990-2009 cars only

ABS Warning Indicator

The Electronic Brake Control Module (EBCM) controls the ABS warning indicator. The EBCM turns the indicator ON for approximately 3 seconds during the engine start up in order to perform a bulb check. The EBCM flashes the ABS warning indicator in order to warn the driver that an ABS malfunction exists, possibly degrading the base brake performance. A solid (not flashing) ABS warning indicator warns the driver that a problem has been detected that affects the operation of the ABS (ABS may be disabled), but normal brake performance will remain. Refer to Antilock Brake System.

Air Bag Warning Indicator

The inflatable restraint diagnostic energy reserve module path sensor (SDM). The SDM will turn the indicator ON for approximately 3 seconds during the engine start up in order to perform a bulb check. The SDM will turn the indicator ON in order to warn the driver of a supplemental inflatable restraint (SIR) electrical system malfunction, possibly affecting the operation of the SIR system. Refer to Supplemental Inflatable Restraint (SIR) System.

Brake Warning Indicator

The brake warning indicator lights under the following conditions:

    • When the master cylinder senses a low brake fluid level
    • When the parking brake switch is closed
    • When certain ABS Diagnostic Trouble Codes (DTC's) are set by the EBCM

The brake warning indicator warns the driver that a base brake problem may exist. Refer to Antilock Brake System.

Charge Warning Indicator

The powertrain control module (PCM) controls the charge warning indicator. The instrument cluster turns the indicator ON during the engine start up in order to perform a bulb check. The powertrain control module (PCM) turns ON the indicator when an undervoltage (11.2 Volts) or overvoltage (16.5 Volts) is detected.

Coolant Warning Indicator

The coolant warning indicator control monitors the engine coolant temperature signal from the engine coolant temperature sensor. The indicator control lights the coolant warning indicator in the following instances:

    • At an engine coolant temperature of approximately 124° C (255° F)
    • At a sender resistance of approximately 53 ohms

Refer to Engine Controls.

Engine Coolant Temperature Gauge

The engine coolant temperature is operated by two coils. The battery voltage is applied to both of the coils. One of the coils is grounded directly and the other coil is grounded through the engine coolant temperature sender. The engine coolant temperature sender has a resistance of 44 ohms at 125° C (260° F). The resistance increases at lower temperatures. The resistance is approximately 1365 ohms at 37° C (100° F), causing the current through the engine coolant temperature sender at one of the coils to increase, as the coolant temperature decreases and moves the pointer.

Fasten Belts Indicator

The seat belt/ ignition key/ lamps alarm controls the fasten belts indicator. The alarm sounds for 4-8 seconds, or until the seat belt is fastened, when the ignition switch is first turned to the RUN position (engine OFF). Refer to Audible Warnings System Check .

Fuel Gauge

The magnetic fields of the two coils moves the fuel gauge pointer. The two coils are at right angles to each other. The battery voltage is applied to the E coil and the circuit divides at the opposite end of the E coil. One voltage path continues to ground through the F coil, as the other goes to ground through the variable resistor of the fuel level sender.

The resistance of the fuel level sender is low when the fuel tank is low. A large flow of current passes through the E coil and the fuel level sender resistor. The current pulls the pointer towards the E on the scale.

The fuel level resistance is high when the fuel tank is full. The increased current flowing though the F coil moves the pointer to the F on the scale. With the two coils operating the pointer, the fuel gauge is not affected by the any changes in the voltage of the system.

High Beam Indicator

Power is supplied to CKT 11 when the headlamps are ON and the headlamp dimmer switch is in the HIGH position, causing the high beam headlamps and the high beam indicator in the instrument cluster to power up. Refer to Lighting Systems.

Low Coolant Indicator

The low coolant indicator receives battery voltage with the ignition switch is in the following positions:

    • RUN
    • BULB TEST
    • START

The instrument cluster will turn the indicator ON for approximately 1 second during engine start up in order to perform a bulb check. The engine coolant level switch grounds the indicator with the coolant level in the coolant reservoir below the minimum recommended level.

Low Fuel Indicator

The powertrain control module (PCM) sends a ground signal to the low fuel indicator in the instrument cluster when the PCM senses a signal from the fuel sending unit indicating a fuel level of approximately 1/8 of a tank. When the signal is recognized by the PCM, the low fuel indicator will light.

Low Oil Level Indicator

The powertrain control module (PCM) controls the low oil level indicator. The PCM samples the oil level once per ignition cycle, at power up only, if the criteria are met, indicating that the oil has had sufficient time to drain into the oil pan from the last power down. If the engine coolant temperature is greater than 75° C (167° F) at power down, the PCM will sample the oil level after 3 minutes have elapsed. If the engine coolant temperature is less than 75° C (167° F) at power down, the PCM will look for at least an 11° C (20° F) drop in the engine coolant temperature, before sampling the oil level at power up.

Oil Pressure Warning Indicator

The oil pressure warning indicator receives battery voltage with the ignition switch in the following positions:

    • RUN
    • BULB TEST
    • START

The instrument cluster turns the indicator ON during the engine start up for a bulb check. The indicator is grounded by the oil pressure indicator switch with a low oil pressure condition.

Perf Shift Indicator

The performance shift switch located on the shift select lever. The performance shift switch is used in order to alter the shift points of the transaxle by sending a signal to the powertrain control module (PCM). At the same time, the signal turns ON the perf shift indicator on the instrument cluster. Refer to Automatic Transaxle/ Transmission.

Service Engine Soon Indicator

The powertrain control module (PCM) controls the service engine soon indicator. Refer to Engine Controls.

Speedometer and Odometer

The vehicle speed sensor (VSS) is a gear driven permanent magnet generator housed in the transaxle. The sensor generates a sine wave output with a frequency proportional to the vehicle speed. The powertrain control module (PCM) converts the signal to an output that switches to ground at a frequency of 4000 pulses per mile. The signal (CKT 389) drives the speedometer and the odometer and is used by various vehicle components.

Tachometer

The tachometer displays the engine speed in RPM's. The voltage pulses are taken from the Powertrain Control Module (PCM) and sent to the tachometer. The tachometer responds to the frequency of the voltage pulses that increase with the engine speed. The solid state circuits process the pulses into a signal that drives the pointer of the tachometer.

Turn Signal Indicators

The turn signal switch is used to control the turn signal lamps. At the same time, the voltage is sent to the instrument cluster in order to turn ON the turn signal indicators. If the emergency flashers are turned ON, both of the turn signal indicators will flash. Refer to Lighting Systems.