Instrument Panel
The operation of indicators described only in this cell is given below. For other indicators, refer to the the Symptom Table. Testing and InspectionSTOP ENGINE TEMP Indicator
The STOP ENGINE TEMP Indicator receives battery voltage from CPS Fuse 5. When the vehicle's engine overheats, the Engine Metal Temperature Switch closes completing a path to ground. The STOP ENGINE TEMP indicator lights and the alarm sounds.
ENGINE OIL Indicator
The ENGINE OIL Indicator receives battery voltage in RUN or START from IGN - ISO Fuse 18. When oil pressure drops below 4 psi the Oil Pressure Switch closes, creating a ground path for the indicator. Before the engine is started and the ignition is in run,the 0il Pressure Switch is closed, providing a bulb test for the indicator.
Fuel Gage
The Fuel Gage uses a three terminal Fuel Level Sensor. One terminal is tied to ground, one terminal is tied to ignition voltage, and the third terminal is the sensing line which is tied to the Body Computer Module (BCM). With a full Fuel Tank, the fuel tank float moves the sensing line voltage close to battery voltage. If the fuel tank is near empty, the fuel tank float moves the sensing line voltage closer to zero. The BCM turns this analog voltage to a digital voltage. This signal is sent to the Instrument Panel Cluster over the serial Data Line.
The BCM also compares the voltage at terminal 3C11 (Fuel Level Reference) to the voltage at terminal 2B8 (Fuel Level Input) so that changes in system voltage do not affect the accuracy of the Fuel Gage.
Speedometer, Odometer and Trip Odometer
The Vehicle Speed Sensor (VSS) is located at the rear of the transmission. The Sensor sends electrical pulses to the ECM at the rate of 40,000 pulses per mile. The ECM buffers this signal and sends it to the BCM. The BCM computes speed and total miles traveled. Seasonal Odometer data is stored in the non-volatile memory. trip Odometer data is stored in the read/write memory. When the Ignition Switch is in RUN, the BCM sends the speed and mileage information to the Instrument Panel Cluster. The mileage memory is in the Body Computer Module (BCM).
PRND321 Display
The Transaxle Position Switch is a series of four mechanical switches that provide a unique code to the Body Computer Module (BCM) for each gear selector position. The BCM interprets this code and, through the Data Line, directs the Instrument Panel Cluster to display the appropriate indicator light.
If the BCM fails to receive this information, code B127 will be set and all gear selector boxes will be lit and flashing.