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 Indicator
- Door Indicator
- Maintenance Required Indicator
- Seat Belt Reminder Indicator
- Tailgate Open Indicator

Refer to each associated system to see its entire schematic.

Coolant Temperature Gauge
The coolant temperature gauge is controlled by the CPU built-in to the gauge assembly. The CPU receives coolant temperature information from the ECM/PCM. The ECM/PCM receives coolant temperature information from the ECT sensor.

Fuel Gauge and Low Fuel Indicator

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 are controlled by the CPU built-in to the gauge assembly. The CPU receives fuel level information from the fuel gauge sending unit.

The fuel gauge sending unit resistance varies from about 19-20 Ohms at full to about 770-790 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 on. When the ignition switch is turned to LOCK (0), the gauge returns to the bottom of the gauge dial regardless of the fuel level.

Speedometer and Odometer
The odometer and the speedometer are controlled by the CPU built-in to the gauge assembly. The CPU receives pulses from the ECM/PCM. 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.