Gauges

SPEEDOMETER
The Speedometer applies voltage to CKT 389. Each time the Vehicle Speed Sensor Buffer (VIN D), or the PCM (VIN L) grounds CKT 389 the Speedometer sees one "pulse." The Vehicle Speed Sensor Buffer grounds CKT 389 to produce a square wave at the rate of 4000 pulses per mile. The Speedometer converts the frequency of the square wave to vehicle speed. A high frequency square wave indicates a high vehicle speed, while a low frequency square wave indicates a low vehicle speed.


FUEL GAGE
A potentiometer is built into the Fuel Sender Assembly. When the Fuel Tank is full, the resistance throughout the potentiometer is approximately 88 ohms, and at empty, the resistance is approximately 1.0 ohms. The Fuel Gage applies voltage through CKT 30 to the potentiometer. As the resistance of the potentiometer decreases, the Fuel Gage senses a smaller voltage drop across the potentiometer, indicating a lower fuel level. As the resistance of the potentiometer increases, the Fuel Gage senses a larger voltage drop across the potentiometer, indicating a higher fuel level.


OIL PRESSURE GAGE (VIN D)
A two position switch opens with oil pressure greater than approximately 24 kPa (3 psi), directing current flow in CKT 231 through a 68 ohm resistor to ground. This causes the Oil Pressure Gage to deflect to approximately 3/4 scale.


OIL PRESSURE GAGE (VIN L)
A variable resistor is part of the Oil Pressure Sender/Fuel Pump Switch. With no oil pressure, the resistance of the variable resistor is approximately 1.0 ohm. At an oil pressure of 550 kPa (80 psi) the resistance of the variable resistor is approximately 88 ohms. The Oil Pressure Gage applies voltage through CKT 231 to the variable resistor in the Oil Pressure Sender/Fuel Pump Switch. As the resistance of the variable resistor increases, the Oil Pressure Gage senses a larger voltage drop across the variable resistor, indicating high oil pressure. As the resistance of the variable resistor decreases, the Oil Pressure Gage senses a smaller voltage drop across the variable resistor, indicating low oil pressure.

COOLANT TEMPERATURE GAGE
The Coolant Temperature Gage applies voltage through CKT 35 to the Engine Coolant Temperature (ECT) Sender and Ignition Switch. The Coolant Temperature Sender is a variable resistor. At 40°C (100°F) the resistance of the Coolant Temperature Sender is approximately 1365 ohms. At 125°C (260°F) the resistance of the ECT Sender is approximately 55 ohms. As the resistance of the ECT Sender decreases, the Coolant Temperature Gage senses a smaller voltage drop across the ECT Sender, indicating higher coolant temperature. As the resistance of the ECT Sender increases, the Coolant Temperature Gage senses a larger voltage drop across the ECT Sender, indicating a lower coolant temperature. When the Ignition Switch is turned to "BULB TEST" or "START," CKT 35 is grounded through the Ignition Switch, causing the gage to indicate high coolant temperature.


"GATE AJAR" INDICATOR
Voltage is applied to the "GATE AJAR" Indicator when the Ignition Switch is in "RUN," "BULB TEST" or "START," through the Gauges Fuse and CKT 39. The RH and LH Liftgate Jamb Switches are closed when the Liftgate is open. When either the LH or RH Liftgate Jamb Switch is closed, the "GATE AJAR" Indicator is grounded through the Jamb Switch and turns "ON."


"ANTI-LOCK" INDICATOR
The Electronic Brake Control Module (EBCM) monitors the Antilock Braking System (ABS). The "ANTI-LOCK" Indicator remains illuminated for three seconds after the Ignition Switch is in the "RUN," "BULB TEST" or "START" position. After this time, the EBCM grounds CKT 1290 to the ABS Lamp Driver Module, causing the Indicator to go out. The system is designed so that a normally functioning system turns the "ANTI-LOCK" Indicator "OFF." The "ANTI-LOCK" Indicator will either flash or illuminate solid in the presence of a fault. A flashing light indicates a problem that will not immediately hamper ABS operation, but should be repaired as soon as possible. A solid light indicates an ABS fault is present and that the vehicle no longer has antilock braking ability. The ABS System must be serviced for full ABS braking capabilities.