Gauges Cluster

FUEL GAUGE
The FUEL Gauge 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 ECM also compares the voltage at terminal 3C4, the Ignition 1 Input (BD50), with the Fuel Level Input BD40 so that changes in system voltage do not affect the accuracy of the FUEL gauge.

VOLTS GAUGE
The BCM monitors system voltage at terminal 3C4, the Ignition 1 input (BD50). This analog voltage is convened to a digital signal and is sent through the Serial Data Line to the IPC.

TEMP GAUGE
The PCM monitors Coolant Temperature at terminal 2B9, the Coolant Temperature Input (EDO4). This analog voltage is convened to a digital signal and sent through the Serial Data Line to the IPC.

OIL GAUGE
The ECM monitors oil pressure at terminal 3C3, the Oil Pressure Input (BD71). This analog voltage is converted to a digital signal and sent through the Serial Data Line to the IPC.

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 PCM at the rate of 40,000 pulses per mile. The PCM buffers this signal and sends it to the BCM. The BCM computes speed and total miles traveled. Seasonal Odometer data is stored in the nonvolatile 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).

TACHOMETER (Mechanical Cluster)
The ignition Module signals the IPC through circuit 121 with varying frequencies which are proportional to engine RPM.

TACHOMETER (Digital Cluster)
Tachometer information is sent to the IPC through the Serial Data Line.

PRND 321 DISPLAY (Digital Cluster Only)
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 Serial 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.