Base

See the circuit referred to for the complete operation of an Indicator and the other components that work with it. Only the Indicators that do not appear in other schematics are described in this section.

Oil Pressure Indicator

The Oil Pressure Indicator comes on to warn the driver when the engine oil pressure is low. Battery voltage is applied to one side of the bulb.A ground path is provided by the Oil Pressure Switch. It closes when the oil pressure is below 27 kPa (4PSI) and the Indicator bulb lights. After the engine starts arid normal oil pressure builds up the Oil Pressure Switch opens. The Oil Pressure Indicator goes out.

Coolant Temperature Indicator

The Coolant Temperature Indicator warns the driver of a high coolant temperature. With the Ignition Switch in RUN, BULB TEST or START, voltage Fuse 11 is applied to the Coolant Temperature Indicator. The bulb is grounded through the Coolant Temperature Switch. The switch closes when the coolant temperature exceeds 258°F (126°C) and the bulb lights.

Upshift Indicator

With the manual Transaxle, a bulb lights when the car should be shifted to the next higher gear for better fuel economy. Battery voltage is applied to one side of the bulb. The other side of the bulb is switched to ground by the ECM which uses engine data such as rpm. vehicle speed arid intake manifold vacuum to compute an efficient shift point.

Service Engine Soon Indicator

The Service Engine Soon Indicator serves as a warning light to tell the driver that a problem has occurred and that the car should be serviced. It is also used by the technician to read out diagnostic codes to help diagnose system problems.

The Indicator receives battery voltage in RUN, BULB TEST, and START. The ECM provides a switched path to ground.

Low Coolant Indicator

The Low Coolant Indicator come on to warn the driver when a low level of coolant exists in the radiator. Battery voltage is applied in BULB TEST and START. The ECM provides a switched path to ground.

Speedometer and Odometer Displays

The Vehicle Speed Sensor (VSS) generates a signal that indicates the speed of the vehicle. The signal is processed by the Solid State ECM to supply inputs to the Trip Computer, Cruise Control Module. Speedometer and Odometer.

The Vehicle Speed Sensor is mounted in the transaxle. A magnet rotates near a coil, producing voltage pulses in the coil. The frequency of the AC voltage coming from this coil depends on the vehicle speed. The VSS sends pulses to the ECM at the rate of 40,000 pulses per mile.

The ECM takes the voltage pulses from the sensor and uses them to close a Solid State output switch. The output terminal is switched to ground at a rate that is proportional to the speed of the car. The Speedometer and Odometers are switched at 4000 pulses per mile.

The Speedometer and the Odometer are operated by a circuit board in the cluster. This circuit board converts the pulses received from the ECM into a control signal for the LCD Displays.

English/Metric Switch

The Speedometer and Odometer Displays can be in either English or Metric. When the English/Metric Switch is depressed the English/Metric Switch input to the cluster is grounded. This ground input to the cluster will enable the cluster to change to the Metric code.

Fuel Gage

The Fuel Gage receives a variable resistance signal from the Fuel Gage Sender. This signal is directly related to the amount of fuel in the Fuel Tank. This variable resistance is an analog signal which is processed by the Instrument Clusters electronics to produce a digital value from 1 to 14 Bars. A resistance of 15 ohms will cause 1 bar to light and flash while 90 ohms will light all 14 bars. The Gage is a Liquid Crystal Display (LCD).