Instrument Panel, Gauges and Warning Indicators: Description and Operation
CLUSTER ILLUMINATIONThe cluster illumination lamps are powered by the panel and interior lamps control switch through the INST LPS fuse and the GRA (8) wire. Ground for the lamps is provided through the BLK (150) wire.
SPEEDOMETER
The speedometer receives an A/C output signal from the digital ratio adapter controller (DRAC) through the LT BLU/BLK (824) wire and converts this to an analog (needle-type) display of vehicle speed.
FUEL GAGE
Power to the fuel gage is supplied through the PNK/ BLK (39) wire with the ignition switch in START or RUN. The movement of the fuel gage needle is controlled by current flowing through two coils in the gage. This movement creates magnetic fields in the coils. The amount of current flowing through each coil is controlled by the fuel tank sender unit. Voltage from the PNK/BLK (39) wire is applied to one end of the EMPTY (E) coil. The other end of the E coil is connected to the FULL (F) coil and BLK (150) wire and the fuel tank sender and PNK (30) wire. (The (30) circuit changes to PPL at C100.) The (30) circuit wire is PPL on the cluster jumper harness.
When the fuel tank is empty the resistance of the fuel tank sender is low (zero ohm). This allows more current to flow through the E coil and the sender resistor and the magnetic field in the E coil pulls the pointer toward E on the fuel gage.
When the fuel tank is full, the resistance of the fuel tank sender is high (90 ohms). This allows more current to flow through the F coil to ground through the BLK (150) wire and the magnetic field in the F coil pulls the pointer toward F on the fuel gage.
OIL PRESSURE GAGE
The oil pressure gage operates the same as the fuel gage. The resistance controlling the current flow through the coils (high coil and low coil) is provided by the oil pressure sender through the TAN (31) wire. With no oil pressure, the resistance of the sender is low (one ohm). At 552 kPa (80 psi), the resistance is high (88 ohms).
COOLANT TEMPERATURE GAGE
The coolant temperature gage also operates the same as the fuel gage and oil pressure gage. Resistance controlling the coils (hot coil and cold coil) is provided by the coolant temperature sender through the DK GRN (35) wire. However, with a coolant temperature of 38°C (100°F), resistance of the sender is high (1365 ohms). With a coolant temperature of 127°C (260°F), resistance of the sender is low (55 ohms).
VOLTMETER
The voltmeter indicates battery voltage with the ignition switch in RUN and the engine not running. With the engine running, the voltmeter indicates generator output.
TACHOMETER
The tachometer displays engine speed in rpm. Voltage pulses are taken from the ignition coil and sent to the tachometer on the 121 (WHT) wire. Solid state circuits process these pulses into a signal that drives the pointer of the meter. The tachometer responds to the frequency of the voltage pulses. These pulses increase with engine speed.
The tachometer has a total range of 0-7000 RPM. The YELLOW warning region has a range of 4750-5250 RPM and the RED warning region has a range of 5250- 7000 RPM.
TURBO BOOST GAGE
The turbo boost gage gets its signal from the manifold absolute pressure (MAP) sensor through the LT GRN (432) and DK GRN (932) wires, The MAP sensor gets a 5-volt reference and a ground feed from the ECM. The MAP sensor reads the manifold pressure and sends a signal voltage between 0 and 5 volts to the turbo boost gage. The voltage is proportional to the manifold pressure.
INDICATOR LAMPS
Power to the ANTILOCK, BRAKE, CHECK ENGINE, CHECK GAGES and LOW TURBO COOLANT indicators is provided through the IGN/GAUGES fuse and the PNK/BLK (39) wire with the ignition switch in START or RUN. Ground for the indicators is provided by various components in the vehicle.
Power to the RIGHT TURN, LEFT TURN, HIGH BEAM and FASTEN SAFETY BELT indicators is provided by various components in the vehicle. Ground is provided to these indicators through the BLK (150) wire.
ANTILOCK INDICATOR
Ground to light the ANTILOCK indicator is provided by the 4-WAL module. When the ignition switch is turned to RUN, the antilock brake module provides a ground for about two seconds through the WHT/BLK (852) wire. This indicates the antilock brake system is operating properly.
BRAKE INDICATOR
Ground to light the BRAKE indicator is provided in one of four ways. When the ignition switch is turned to RUN, the antilock brake module provides a ground to the indicator for about two seconds through the TAN/WHT (33) wire. This indicates the antilock brake system is operating properly. If a malfunction occurs in the hydraulic portion of the four-wheel antilock brake system, the BRAKE indicator will light.
The BRAKE indicator will light when the parking brake is set. This closes the parking brake switch providing a ground to the BRAKE indicator.
If a brake hydraulic circuit loses pressure, the brake pressure warning switch closes, providing a ground to the BRAKE indicator.
CHECK ENGINE INDICATOR
The CHECK ENGINE indicator will light if a problem is detected with the engine running and the vehicle moving.
CHECK GAGES INDICATOR
The CHECK GAGES indicator lights to alert the driver to a low oil pressure or high coolant temperature condition. The signals from the engine coolant temperature sender and the engine oil pressure sender are monitored by the CHECK GAGES lamp driver. The lamp driver controls the ground to the CHECK GAGES indicator mounted in the instrument cluster.
FASTEN SAFETY BELT WARNING INDICATOR
Battery voltage is applied to the FASTEN SAFETY BELT warning indicator for four to eight seconds when the ignition switch is in RUN, BULB TEST or START, by the YEL (237) wire from the convenience center.
DIRECTIONAL INDICATORS
Power to the directional indicators is provided by the directional switch or hazard switch. The LH indicator is powered through the LT BLU (14) wire. The RH indicator is powered through the DK BLU (15) wire.
HIGH BEAM INDICATOR
Power to the high beam indicator is provided by the LT GRN (11) wire with the headlamps on and the dimmer switch in Hi position.
LOW TURBO COOLANT WARNING INDICATOR
Ground path is provided by the LT GRN (904) wire to the coolant level sender. The lamp will light to indicate a low coolant condition in the charge air cooler radiator.