The coolant temperature sending unit is mounted to the engine. The unit is mounted at a point where the unit is exposed to the coolant being circulated through the engine coolant passages. The sending unit contains a temperature-sensitive variable resistor that senses and reacts to coolant temperature. Resistance decreases as temperature increases.

When electric power is supplied to the engine coolant temperature gage, current flows through the gage. The current flows to the variable resistor and then to a ground at the engine. The position of the gage pointer is determined by the strength of the current flowing through the gage. When the engine coolant is cold the following situations exist:

As the coolant temperature increases, the following situations occur:

Prolonged driving or idling in very hot weather may cause the pointer to move beyond this point. An overheat condition exists if the pointer goes into the red zone at the upper limit of the scale.

Dial calibrations go far above the normal boiling point of water, which is 100°C (212°F). This is because the cooling system is pressurized. The increase in pressure also increases the boiling temperature of the coolant. This action permits the coolant to reach temperatures above those possible with a non-pressurized system without boiling. The higher operating temperature of the cooling system that results gives greater cooling efficiency and other benefits.

The fuel gage sending unit is mounted on the top surface of the fuel tank. The fuel level sender itself consists of the following two components:

When electric power is supplied to the fuel gage, current flows through the gage to the variable resistor and then to a ground. The position of the gage pointer is determined by the strength of the current that is flowing through the gage.

If the tank is full the following situations occur:

If the fuel level is low the following situations occur:

Intermediate fuel levels cause the pointer to indicate the corresponding position between F and E.

The oil pressure gage indicates the pressure of the lubricating oil flow provided by the engine oil pump. The oil pressure gage sending unit is a variable resistor that is mounted to the engine block. The sending unit senses the oil pressure in a main oil passage just downstream from the engine oil pump. When electric power is supplied to the gage, current flows through the gage to the resistor in the sending unit and then to the ground at the engine block. The position of the oil pressure gage pointer is determined by the strength of the current flowing through the gage.

When oil pressure is low the following situations exist:

As oil pressure increases the following situations occur:

Under normal conditions the oil pressure reading should be measure 138-414 kPa (20-60 psi). Engine oil pressure should never fall below a reading of 28 kPa (4 psi), even at idle.

The electric speedometer does not have a speedometer cable. The source of speed information is a small permanent magnet alternating current generator called a vehicle speed sensor (VSS). The VSS is mounted on the transmission. The shaft of the VSS fits into rotor teeth on the transmission output shaft in the same manner as the speedometer cable of a mechanical speedometer system. The transmission output shaft rotates and turns the rotor teeth near a magnetic pick-up within the VSS. This generates an alternating current in the coil with a frequency that is proportional to the speed of the vehicle.

The alternating current from the VSS is sent to the powertrain control module (PCM).

The PCM modifies the current to a series of direct current pulses at a frequency proportional to the speed of the vehicle. These pulses form a vehicle speed signal that is transmitted to the speedometer.

At the speedometer, a solid state circuit uses the speed signal in order to regulate the distribution of the current from the fuse block to 2 electromagnetic coils. The magnetic coils are at right angles to each other, near the base of the speedometer pointer pivot. At the base of the speedometer pointer pivot is a magnet that is acted upon by the magnetic fields of the 2 coils. The relative strength of the 2 magnetic fields determines the position of the magnet and accordingly, the position of the speedometer pointer.

Pulses from the solid state circuit also are used in order to drive a small electric stepper motor. The stepper motor turns the numbered wheels of the odometer and the trip odometer. The numbered wheels are geared so that when any one wheel completes a revolution, the next wheel to the left is turned one-tenth of a revolution. Every tenth of a revolution advances the displayed number by one unit. The trip odometer can be reset to zero at any time. This allows the driver to record the distance traveled from any selected starting point.

The tachometer signal comes from the PCM. The tachometer displays the engine speed in thousands of revolutions per minute (rpm).

The voltmeter is an instrument that shows the voltage of the vehicle electrical system. The voltmeter indicates the ability of the charging system to keep the storage battery charged. The voltmeter is wired in parallel with other circuits in the vehicle.

When the engine is running the voltmeter indicates charging system voltage. If the engine is not running and the ignition switch is in the RUN or START position the voltmeter will show battery voltage. The voltmeter can be used as a first step in diagnosing many electrical problems. Battery voltage drop can be seen while the engine is cranking. After the engine is running, generator output voltage is indicated.

The voltmeter should read between 11-13 volts during extended idle or just after starting. As the electrical load is increased, or in stop-and-go driving, the pointer may rotate temporarily to the bottom of the scale. A voltmeter reading continuously below 11 volts or above 16 volts indicates an electrical system problem.