Document ID# 1206210
1998 Saturn SL2/SC2/SW2
 

Instrument Panel Cluster (IPC) Description and Operation

Instrument Panel Cluster

The instrument panel cluster (IPC) is used to communicate information on the operation and performance of the vehicle to the driver. The cluster is comprised of analog gages, including a tachometer, which are accurate, precise, easy to read, and well lit. The cluster also contains an assortment of telltale indicator lamps which signal the operation or malfunction of certain key systems.

Speedometer/Odometer

The speedometer receives vehicle speed information from the PCM. The vehicle speed signal is passed through an RC filter to the input of the speedometer/odometer driver integrated circuit (IC), located in the I/P cluster. The high-to-low edge of the square wave input triggers the IC to provide a well defined pulse of current to the coil of the speedometer gage. The IC also counts the input transitions and uses this information to drive the odometers. The vehicle completes one mile for every 5000 pulses received from the PCM.

There are 2 odometers in the I/P cluster. The odometer shows total mileage since the vehicle was built and cannot be reset. The trip odometer which shows total mileage since last reset, and can be synchronized. This means that even though one of the odometers may advance by a mile/kilometer the other one may or may not advance to the next mile/kilometer at the same time. The odometer is back lit by a single bulb to make it easier to read in all lighting conditions.

Important

The odometer always powers up in the season odometer mode, regardless of which mode was selected before turning ignition OFF

Important

The odometer mileage remains readable for several minutes after ignition is turned OFF.

The button located next to the odometer allows you to switch from odometer (6-digit display) to trip odometer (4-digit display). By pressing this button, you can toggle between the odometer to zero, select trip odometer and hold the button in for one to two more seconds.

Tachometer

The tachometer is controlled by the powertrain control module (PCM) using a pulse width modulated (PWM) signal based on the signal received from the crankshaft position (CKP) sensor. The PWM signal to the cluster is passed through an RC filter and sent to the tachometer driver integrated circuit (IC). The high-to-low edge of the PWM signal triggers the IC to provide a well defined pulse of current to the coil of the tachometer. the engine completes one revolution for every six pulses received from the PCM. The PCM monitors circuit 121 for an open, short to ground or short to voltage and will set DTC P1693 if certain parameters are met.

Fuel Gauge

The fuel gage is controlled by the PCM using a pulse width modulated (PWM) signal based on the signal received from the fuel level sensor. The duty cycle of the PWM signal is directly related to the reading of the fuel level sensor. As the duty cycle increases the fuel level reading displayed by the gage will increase. The PWM signal to the cluster is passed through an RC filter and sent to the fuel gage. The PCM monitors circuit 455 for an open, short to ground, or short to voltage and will set DTC P0656 if certain parameters are met.

Coolant Temperature Gage

The coolant temperature gage is controlled by the PCM using pulse width modulated (PWM) signal based on the signal received from the engine coolant temperature (ECT) sensor. The duty cycle of the PWM signal is directly related to the reading of the fuel level sensor. As the duty cycle increases the fuel level reading displayed by the gage will increase. The PWM signal to the cluster is passed through an RC filter and sent to the fuel gage. The PCM monitors circuit 455 for an open, short to ground, or short to voltage and will set DTC P0656 if certain parameters are met.

Daytime Running Lamps

The DRL logic is not separately replaceable from the I/P cluster. The purpose of the DRL is to make the vehicle more visible during daylight hours and at dusk and dawn. This is achieved by having the high beam headlamps ON at half intensity. The half intensity of the high beam headlamps is accomplished by switching the DRL relay ON, which connects the high beam headlamps in series.

The DRL logic controls the HI beam telltale, DRL ON telltale and the DRL relay. The DRL relay is used to provide control of the high beam headlamps.

When the park brake is applied an input is provided to the DRL logic. This signals the DRL logic to turn DRL OFF. DRL will also turn OFF if the low beam headlamps are turned ON.

Powertrain Control Module (PCM)

The PCM controls the SERVICE ENGINE SOON telltale indicator lamp, (also called the malfunction indicator lamp [MIL]), SERVICE (Wrench), coolant temp/low coolant/auto trans fluid temp, LOW FUEL telltale indicator lamps. It controls these telltale indicator lamps by pulling the control circuit to ground. When the circuit is pulled to ground, the telltale indicator lamp is turned ON.

The PCM also supplies the speed signal input to the integrated circuit (IC), located in the instrument cluster, for control of the speedometer and odometer. The PCM receives a vehicle speed input from the vehicle speed sensor.

In addition the PCM also controls the tachometer, fuel gage, and coolant temperature gage based on inputs from the crankshaft position sensor, fuel level sensor, and engine coolant temperature sensor respectively.

ABS Control Module

The ABS control module controls the ABS telltale indicator lamp. TRACTION ACTIVE telltale , and is one of three inputs that control the BRAKE telltale indicator lamp.

The ABS control module controls the ABS telltale lamp indicator through telltale control logic in the intermittent cluster. When the ABS control module grounds the input of the cluster, the telltale control logic is OFF and the ABS telltale indicator lamp is OFF. If the ABS control module ungrounds the circuit, or the circuit becomes open and ignition voltage is present at the cluster, the telltale control logic turns ON and the ABS telltale indicator comes ON. The ABS control module turns ON the ABS telltale indicator lamp if it senses a possible problem in the electronics of the ABS.

Oil Pressure Switch

The oil pressure switch is a normally closed switch that opens with normal engine oil pressure. The switch opens with oil pressure after the engine is started. The switch closes when oil pressure drops below a specified limit. With the contact set closed a ground is supplied for the oil pressure telltale indicator lamp, allowing it to come ON.

Headlamp Switch

The headlamp switch supplies a ground, through circuit 1200E, to the DRL logic whenever the switch is in the high beam or flash-to-pass position. With a ground supplied to the DRL logic the high beam telltale will be turned ON.

The headlamp switch supplies a ground, through circuit 1201H, to the DRL logic whenever the switch is in the low beam position. With a ground supplied to the DRL logic, DRL will be turned OFF.

Turn and Hazard Switches

The turn and hazard switches supply a power signal to the right and left turn signal telltale indicator lamps whenever the operator of the vehicle turns ON the turn signals. This signal passes through a flasher module, which turns the signal ON/OFF causing the turn signals and turn signal telltale indicator to flash. If the hazard flashers are turned ON, the signal is passed through the same flasher module, and all turn signal lamps and turn signal telltale indicators will flash indicating the hazard flashers are ON.

Low Brake Fluid Switch

The low brake fluid switch closes when brake fluid drops below a specified limit. With the switch closed a ground is supplied for the brake telltale indicator lamp, allowing it to come ON.

Park Brake Switch

The park brake switch is mounted on the parking brake lever mounting bracket and is closed when the park brake is engaged. With the switch closed, a ground is supplied for the brake telltale indicator lamp, allowing it to come ON.

Generator/Voltage Regulator

The generator and voltage regulator (one assembly) pulls to ground the charge (battery) telltale indicator lamp if there is a problem in the charging system. This problem could be in the generator, voltage regulator, battery, or associated wiring.


  Document ID# 1206210
1998 Saturn SL2/SC2/SW2