Circuit Operation - Gauges and Warning Indicators

The Instrument Cluster contains analog gages, indicators and a Digital Display. Their operation is described as follows:

Tachometer
The Tachometer displays engine speed in rpm. Voltage pulses are taken from the Ignition System and sent to the Tachometer. It responds to the frequency of the voltage pulses which increase with engine speed. Solid State circuits process these pulses into a signal that drives the pointer of the meter.

Oil Pressure Gage
The engine oil pressure is displayed by the Oil Pressure Gage. The pointer of the Gage is moved by two coils.

The Oil Pressure Sensor is connected to the junction of the two coils. It has low resistance when the oil pressure is low, and 90 ohms resistance when the oil pressure is high. This changing resistance changes the current flow through the coils. The magnetic fields of the coils move the pointer.

Coolant Temperature Gage
The Coolant Temperature Gage is also operated by two coils. Battery voltage is applied to both coils. One is grounded directly and the other is grounded through the Engine Gage Coolant Temperature Sensor. This has 55 ohms resistance at 260°F (hot coolant) and its resistance increases at lower temperature. Resistance is approximately 1400 ohms at 38°C (100°F). This causes the current through the sender and one coil to increase as the coolant temperature increases. This moves the pointer.

Voltmeter
The Voltmeter measures the electrical system voltage with the Ignition Switch in "RUN," "BULB TEST" or "START." With the Engine stopped, the Voltmeter indicates Battery condition. With the Engine running, the Voltmeter indicates Charging System voltage.

Fuel Gage
The Fuel Tank Sending Unit contains a variable resistor which changes resistance corresponding to fuel in the tank (0 ohms - empty, 90 ohms - full). This signal is sent to the Central Control Module (CCM), where it is filtered and sent to the Instrument Cluster.

Oil Temperature Gage
The operation of the Oil Temperature Gage is identical to the operation of the Coolant Temperature Gage. One of the coils of the gage is grounded through the Engine Oil Temperature Sensor. The variable resistance of the sensor operates exactly the same way as the Engine Coolant Temperature Sensor. This has 26 ohms resistance full hot (VIN P) or 38 ohms (VIN J).

"SECURITY" Indicator
Refer to Theft Deterrent System. Antitheft and Alarm Systems

High Beam Indicator
The High Beam Indicator has Battery applied to one side with Ignition "ON." The CCM will ground the other side of the indicator when the HI/LO Beam Switch is activated for High Beams.

"FASTEN SEAT BELT" Indicator
Refer to Warnings And Alarms. Audible Warning Device

"CHANGE OIL" Indicator
The CCM will ground one end of the "CHANGE OIL" Indicator, illuminating it at the proper oil change intervals.

"CHECK GAUGES" Indicator
The CCM will illuminate the "CHECK GAUGES" Indicator by grounding one side of the indicator bulb when:
1. The Oil Temperature Gage is above the normal operating temperature range.
2. The Coolant Temperature Gage is above the normal operating range.
3. The fuel level is too low.
The "CHECK GAUGES" Indicator will turn "OFF" when ranges return to normal.
The "CHECK GAUGES" Indicator will also be illuminated by an Oil Pressure Switch that grounds the indicator bulb when a low oil pressure (below 2 psi) condition exists.

"ONE-TO-FOUR" Indicator
The Engine Control Module (ECM) will illuminate a bulb by grounding one side of it when a One-To-Four Condition exists. Refer to Powertrain Management. Powertrain Management

"BRAKE" Indicator
Refer to Brake Warning System. Brake Warning Indicator

"DOOR AJAR" Indicator
The "DOOR AJAR" Indicator will illuminate if Ignition is "ON" and one or both of the doors are opened. Ground is applied to one side of the indicator bulb through the Diode Module. The Diode Module receives ground through either LH or RH Door Ajar Switch.

The purpose of the Diode Module is to isolate the LH and RH Door Ajar Switches while being able to use one indicator. Do not confuse this Diode Module with the one used for the Coupe Cargo Lamps.

Digital (LCD) Display
The Digital Display is completely controlled by the CCM, including Power, by way of seven data lines between the CCM and the Instrument Cluster. If there is a problem with any of these data lines, the CCM will set a Diagnostic Trouble Code (DTC).

The Digital Display indicates the vehicle speed, the fuel level, the trip and season odometers, fuel data, trip data and System Malfunction indication. Also DTCs set by the CCM are indicated on the Digital Display. Refer to Central Control Module. Central Control Module

If the Digital Display malfunctions, DTCs may be read by using a Tech 1.

The backlighting of the Digital Display is controlled also by the CCM.