Digital Cluster

CIRCUIT OPERATION

The operation of an individual indicator is described along with its circuit. Refer to the schematic and text for the circuits described below.

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 88 ohms; with an empty tank, the resistance is near 0 ohms. The instrument cluster electronics converts the analog signal from the fuel gage sender to a digital signal that controls the vacuum fluorescent fuel gage display.

Temperature Display
The digital engine coolant temperature sensor provides a signal to the instrument cluster that is related to the engine coolant temperature. With the engine coolant at 38°C (100°F), the sensor resistance is 1365 ohms. When the engine coolant reaches a temperature of 127°C (260°F), all bars light. The temperature gage display receives its signals through the instrument cluster, which is connected to the digital engine coolant temperature sensor.

Speedometer and Odometer
The vehicle speed sensor (VSS) generates a signal that indicates the vehicle speed. The signal is processed by the solid state powertrain control module (PCM) to supply inputs to the speedometer and the odometer.

The vehicle speed sensor is mounted in the transaxle, and generates an AC voltage signal with a frequency proportional to vehicle speed.

The PCM takes the 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 vehicle speed. The speedometer and odometer are switched at the same frequency that the sensor generates.

The speedometer and odometer are operated by a circuit board in the cluster. This circuit board converts the pulses received from the PCM into a control signal for the vacuum fluorescent displays.

Driver Information Center (DIC)
The instrument cluster has within it a 20 character vacuum fluorescent display that conveys information concerning various vehicle systems to the driver. The driver information center (DIC) display is part of the instrument cluster, and uses discrete and serial data inputs to provide vehicle information to be processed by the DIC. The DIC messages are accompanied by a chime within the instrument cluster. The DIC displays the following:

Date/time information
Oil level warning
Oil life information and warning
Oil pressure information and warning
PCM data line problem
Park Brake on warning
Door ajar information
Lamp Monitor warning
Tachometer information and warning
Trip computer information
PASS-key II warning information
Fuel level information and warning
Charge system warning
Coolant temperature warning and information
Battery voltage information and warning
Coolant level warning
Diagnostic information

Date/Time
Date and time information are retained within the DIC via use of the hot at all times feed to the instrument cluster.

Oil Level Warning
The DIC CHECK OIL LEVEL message is displayed to alert the driver of a low oil level condition. The low oil sensing circuit consists of an oil level module and low oil level sensor. This system is active only at initial engine starting and not while the engine is running. The oil level is measured if the engine has been off long enough for top engine oil to have returned to the oil pan.

The oil level module receives battery power at all times to retain memory of engine on and off times. If the ignition on input has been at 0 volts for at least 8 minutes, the oil level module activates the low oil level sensor. If the sensor returns a signal indicating a low oil condition, the DIC displays CHECK ENGINE OIL 15 to 25 seconds after the ignition switch is turned to RUN. If the ignition switch is turned off for less than 20 seconds, the oil level module remembers and sends the previous oil level status to the DIC and ignore the present oil status. If the ignition switch has been OFF for more than 20 seconds, but less than 8 minutes, the oil level module ignores the low oil level sensor.

Oil Life Information
The DIC receives engine information over the serial data line from the PCM. The DIC uses this information to calculate remaining engine oil life. When the remaining oil life is low, the DIC displays the appropriate message. If the OIL button is pressed, the DIC displays remaining oil life.

Oil Pressure Information
The oil pressure information is received from the oil pressure sensor/switch. The oil pressure may be displayed by pressing the GAGE button. If the pressure is low, the OIL PRESSURE LOW message is displayed.

Park Brake On Warning
If the park brake is left applied and the gear selector lever is not in PARK or NEUTRAL, the park brake input terminal is grounded. The PARK BRAKE ON message is displayed and a fast chime briefly sounds.

Door Ajar Warning
The door ajar information is received from discrete door switch inputs. When the corresponding input is grounded and the gear selector lever is not in PARK or NEUTRAL, the associated message is displayed.

Lamp Monitor Warnings
Lamp outage information is received over the lamp monitor serial data line.

Trip Computer Information
Trip computer information, such as instantaneous fuel usage, is received over the serial data line from the PCM. A discrete input sends fuel level information for range calculations. This raw data is processed by the DIC using its internal time keeping functions to determine, for example, average fuel economy.

PASS-Key II Information
The PASS-Key II information comes over the serial data line from the PCM.

Fuel Level Information
The fuel level information is received from the fuel gage sender. When the DIC calculated range falls below 60 miles, the LOW FUEL RANGE message is displayed. FUEL LOW is displayed when fuel level is below 2.5 gallons.

Coolant Temperature Information
Coolant temperature information is received over the serial data line from the PCM. The coolant temperature may be displayed by the DIC. If the coolant temperature rises above 127°C (261°F), the HOT...STOP ENGINE message is displayed.

Battery Voltage Information
Battery voltage information is received over the serial data line from the PCM. If the battery voltage exceeds 16.0 volts or falls below 10.5 volts, the BATTERY VOLTS HIGH or BATTERY VOLTS LOW message is displayed.

Coolant Level Information
Coolant level information is received from the low coolant module, which receives power with the ignition switch in RUN. When the low coolant module senses low coolant level, it grounds the input to the instrument cluster. The DIC displays the COOLANT LEVEL LOW message.

PCM Data Line Information
If the data line to the PCM fails, the DATA LINK PROB message is displayed.

Charge System Warning
If the generator input is grounded for 10 seconds, the CHECK CHARGE SYSTEM message is displayed.

Oil Pressure Indicator
When oil pressure drops below 10 psi, the instrument cluster turns on the OIL indicator in response to the oil pressure sender/switch resistance.

LIGHTS ON Indicator
The LIGHTS ON indicator receives battery voltage with the park lamps or headlamps on. The indicator low side is tied to cluster internal ground.