Brake Warning Indicator: Description and Operation

Circuit Description

Speedometer
With the ignition switch in ON and START, the speedometer drive circuits receive pulse from the vehicle speed sensor (VSS). The pulse rate increases as the car accelerates. The frequency and duration of these input pulses are measured and displayed by the speedometer.

Tachometer
The tachometer displays engine speed in rpm. Voltage pulses are taken from the ignition system and sent to the tachometer. The tachometer responds to the frequency of the voltage pulses, which vary according to engine speed. The ECM processes these pulses into a signal that causes the gauge's is needle to move. Check Engine & Oil Pressure Indicator Battery voltage is applied to the indicator bulb from fuse 2 with the ignition switch in ON or START. The ground of the check engine indicator is controlled
by the engine control module.

The control module will light the indicator when the engine is not running or when it detects a problem. When the oil pressure is low, the oil pressure switch closes, providing a ground for the oil pressure indicator bulb.

Fuel Gauge & Indicator
The pointer of the fuel gauge moves by the magnetic field of two coils. The coils are at right angles to each other. Battery voltage is applied to the coils through fuse 2, generating a magnetic field. The magnetic field, controlled by the fuel gauge sender, causes the gauge's needle to move. As the resistance in the sender varies, current through the gauge coils change. When the fuel level is below the thermistor, the resistance of the thermistor varies, providing a ground for the low fuel indicator bulb.

Engine Coolant Temperature Gauge
The pointer of the engine coolant temperature gauge moves by the magnetic field of two coils. The coils are at right angles to each other. Battery voltage is applied to the coils through fuse 2, generating a magnetic field. The magnetic field, controlled by the engine coolant temperature sender, causes the gauge's needle to move. As the resistance in the sender varies, current through the gauge coils change.