Instrument Panel, Gauges and Warning Indicators: Description and Operation

Gauges and Indicators

How the Circuit Works
The indicators are controlled by relative conditions in their associated systems. For the following indicators the information supplied to the gauge assembly is received via the multiplex control unit:
- Charging System
- Door/Hatch Indicator Light
- Maintenance Required Indicator
- Seat Belt Reminder

Refer to each associated system to see its entire schematic.

Engine Coolant Temperature Gauge
The engine coolant temperature gauge is controlled by the CPU built-in the gauge assembly. The CPU receives coolant temperature information from the ECM/PCM via the multiplex control unit. The ECM/PCM receives coolant temperature information from the ECT sensor.

Fuel Gauge and Low Fuel Indicator Light

WARNING: Do not smoke while working on the fuel system. Keep open flame away from the work area. Drain fuel only into an approved container.

The fuel gauge and low fuel indicator light are controlled by the CPU built-in the gauge assembly. The CPU receives fuel level information from the fuel gauge sending unit.

The fuel gauge sending unit's resistance varies from about 11-13 ohms at full to about 130-132 ohms at empty. The fuel level signals current changes with the varying resistance, which enables the CPU to determine the level of the fuel. When the CPU determines that the fuel level is low, it turns the low fuel indicator light on. When you turn the ignition switch to LOCK (0), the gauge returns to the bottom of the gauge dial regardless of the fuel level.

Speedometer and Odometer
The odometer circuit drive and the speedometer are controlled by the CPU built-in the gauge assembly. The CPU receives pulses from the vehicle speed sensor. The pulse rate increases as the car accelerates. The frequency and duration of these input pulses are measured by the CPU.

Tachometer
The tachometer is controlled by the CPU built-in the gauge assembly. The CPU receives pulses from ECM/PCM. The pulse rate increases as the engine speed increases. The frequency and duration of these input pulses are measured by the CPU.