Gages (UB3)

The operation of an Indicator is explained in the operation of its circuit. See the circuit referred to for complete operation of an Indicator and the other components that work with it. Only the Gages and Indicators that do not appear in other schematics are described in this section.

FUEL DISPLAY

The Fuel Gage sender provides a signal to the Instrument Cluster that is related to the fuel level. With a full tank the Fuel Gage Sender resistance is 90 ohms, and with an empty tank the resistance is less than 1 ohm. The Instrument Cluster electronics convert the analog signal from the Fuel Gage Sender to a digital signal which controls the LCD Fuel Gage Display.

TEMPERATURE DISPLAY

The Coolant Temperature Sender provides a signal to the Instrument Cluster that is related to the engines temperature. With the engine at 140°F, the sender resistance is 567 ohms and two bars are lit. When the engine reaches a temperature of 260°F (77 ohms) all 10 bars will light. When the ninth bar lights. the High Coolant Temperature Display will light. The Temperature Gage Display receives its signals through the Instrument Cluster, which is connected to the Coolant Temperature Sender.

OIL PRESSURE DISPLAY

The Fuel Pump/Oil Pressure Switch/Sender provides a signal to the Cluster that is related to the Oil Pressure. At 80 PSI, all 10 bars are lit and the sender has a resistance of 80 ohms. When the bar graph changes form 3 to 2 segments, the Low Oil Pressure Indicator lights. The Oil Pressure Display receives its signals through the Instrument Cluster which is directly connected to the Fuel Pump/Oil Pressure Switch/Sender.

VOLTS DISPLAY

The Instrument Cluster receives battery voltage from the incoming power leads. The Instrument Cluster's internal circuity converts the analog voltage to digital voltage where it is displayed by the Volts Gage. At 8 volts, the first bar is illuminated. When the ninth bar is turned on, or second bar turned off, the Charge Indicator is lit.

TACHOMETER DISPLAY

The Tachometer Display contains both digital and analog displays. The digital display indicates "0" at zero rpm, has a 10 rpm resolution below 1000 rpm. and 100 rpm resolution above 1000. The analog display has numerals, "RPM" and the first bar is always lit when the cluster is turned on (even when the engine is stopped).

The Tachometer data is supplied to the cluster on the Serial Data Link.

PRNDL DISPLAY

The PRNDL Display consists of 7 indicators, Park, R, N, D, 2, 1, Automatic Overdrive (Four Speed Automatic) Gear selection is shown by the illumination of a rectangular box around the appropriate letter. The Indicator will not skip gear positions during gear selection but will light each box sequentially until the desired gear position is shown.

The PRNDL Display receives its input from the PRNDL Switch, The input consists of a 4-bit coded word. When an invalid input is applied, the PRNDL display will flash on and off for one minute. After one minute, all Gear Selector positions will remain illuminated to indicate a system error.

SERVICE ENGINE SOON INDICATOR

The SERVICE ENGINE SOON Indicator serves as a warning light to tell the driver that a problem has occurred and the car should be serviced. It is also used by the technician to read out diagnostic codes to help diagnose system problems.

The Indicator receives battery voltage in RUN, BULB TEST and START, the ECM provides a switched path to ground.

LOW COOLANT INDICATOR

The Low Coolant Indicator comes on to warn the driver when a low level of coolant exists in the radiator. Battery voltage is applied in RUN, BULB TEST and START. The ECM provides a switched path to ground (V6 VIN T) (see Computers and Control Systems) or ground is provided through the closed contact of the Coolant Level Sensor (V6 VIN L).

SEASON/TRIP SWITCH

Depressing the Season/Trip Switch will display the Trip Odometer. Depressing the Season/Trip Switch again. After the Trip Odometer is displayed and holding for at least 2 seconds resets the Trip Odometer to zero.

Tapping or depressing the Season/Trip Switch less than 1.5 seconds with the Trip Odometer displayed) returns the display to the Season Odometer.

SPEEDOMETER and ODOMETER DISPLAYS

The Vehicle Speed Sensor (VSS) generates a signal that indicates the speed of the vehicle. The signal is processed by the Solid State ECM to supply inputs to the Cruise Control Module, the Speedometer and the Odometer.

The ECM takes voltage pulses from the sensor and uses them to close a Solid State output switch, The output terminal is switched to ground at a rate that is proportional to the speed of the car. The Speedometer and Odometer are switched at the same frequency that the sensor generates, 4000 pulses per mile.

The Speedometer and Odometer are operated by a circuit board in the cluster. This circuit board converts the pulses received from the ECM into a control signal for the LCD Displays.

Each time the Ignition is turned on, the cluster will display the Season Odometer.

ENGLISH/METRIC SWITCH

The Speedometer, Odometer, Oil Pressure Display and Temperature Display can be either English or Metric. When the English/Metric input to the cluster is grounded, the Instrument Cluster displays Metric values. When the switch is open, the Instrument Cluster displays English values.