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Instrument Cluster / Carrier: Description and Operation

Instrument Cluster

The instrument cluster contains gauges, indicator lamps and warning lamps that are designed to provide the driver with system status and to alert the driver that certain conditions exist in the vehicle. Gauges provide information to the driver indicating the status of systems. Examples of systems that use gauges include vehicle speed, fuel level, engine coolant temperature, and engine rpm. Indicator lamps provide information to the driver of conditions that exist in the vehicle. Examples of the indicator lamps include the turn signal, low washer fluid level, traction control, and speed control. Warning indicator lamps provide information to the driver of conditions that could potentially alter vehicle performance. Examples of the warning indicators include the ABS, BRAKE, safety belt, and low oil pressure.

Principles of Operation

NOTE: The instrument cluster, front electronic module (FEM), and the rear electronic module (REM) must be reconfigured upon installation.

NOTE: The diagnostic tool may display ICM for the instrument cluster.

NOTE: For any concerns with the restraint control module (RCM).

NOTE: The instrument cluster is not repairable at the dealership with the exception of the instrument cluster lens. Do not disassemble the instrument cluster.

The instrument cluster is a hybrid electronic instrument cluster (HEC). The vehicle electronic functions are divided into zones. The instrument cluster, FEM, and REM use the standard corporate protocol (SCP) communication network to transmit and receive information. It is very important to understand:

- where the input (command) originates from.

- all information (messages) necessary in order for a feature to operate.

- which module(s) receive(s) the input or command message.

- whether the module which received the input (message) controls the output of the feature, or whether it outputs a message over the SCP communication network to another module.

- which module controls the output of the feature.

The instrument cluster communicates with the FEM, REM, anti-lock brake system/traction control (ABS/TC), powertrain control module (PCM), and the RCM over the SCP communication network to control the gauges, indicators, and chimes.

The instrument cluster carries out a display prove-out to verify the integrity of the cluster controlled indicators. When the key is in the ON position with the engine OFF, the following warning indicators will prove out:

- BRAKE warning indicator

- anti-lock brake system (ABS) warning indicator

- engine over-temperature warning indicator

- traction control low fuel indicator

- low washer fluid warning indicator

- CHECK FUEL CAP indicator

There are three indicators that also maintain a prove-out but are controlled by other modules. The air bag warning indicator prove-out is controlled by the RCM, the check engine indicator is controlled by the PCM and the charging system warning indicator is controlled by the PCM.

Integrated Circuit Display

The integrated circuit display is a fluorescent vacuum tube display that maintains three separate functions housed in a single display area, the warning center display, the trip NB and odometer display, and the PRNDL display.

Warning Center Display

The warning center display alerts the driver of a lamp outage condition and is contained in the integrated display. The FEM and REM both control the exterior illumination. when an exterior lamp(s) is inoperative, the FEM or REM notify the instrument cluster over the SCP communication network and the instrument cluster illuminates the warning center message LAMP OUT. The warning center message will remain on until the condition is corrected. Once the condition is corrected, the warning center will return to the trip odometer display.

Trip A/B And Odometer Displays

The vehicle speed signal (VSS) from all four wheels is hardwired directly to the ABS/TC. The vehicle speed rolling count status is then sent to the instrument cluster by the ABS/TC over the SCP communication network.

PRNDL Display

The digital transmission range (TR) sensor is hardwired directly to the PCM. The status of the gear selection is sent to the instrument cluster from the PCM over the SCP communication network.

Gauges

Fuel Gauge

The fuel gauge system has a saddle-type fuel tank with two integrated fuel senders: the fuel delivery module and the jet pump module. The fuel delivery module is located in the right side of the fuel tank and the jet pump module is located in the left side of the fuel tank. Fuel level status is sent directly to the REM, which is hardwired to the fuel senders. The REM sends the fuel data to the instrument cluster via the SCP line. Normal operating range of the fuel delivery module is from 16 +/- 2 ohms at empty (E) to 155 +/- 4 ohms at full (F). Normal operating range of the jet pump module is from 19 +/- 2 ohms at empty (E) to 160 -/+ 2 ohms at full (F). If the jet pump module is open, the fuel gauge will default to the fuel delivery module sender value only and the fuel gauge will indicate E to 1/2 tank (depending on the fuel level on the fuel driver module side of the tank). If the fuel delivery module is open, the fuel gauge will default to the empty (E) position.

Speedometer Gauge

The instrument cluster uses a vehicle speed signal from the ABS/TC system to control the movement of the speedometer pointer. Vehicle speed information is sent to the ABS/TC module from all four wheel speed sensors, which is then sent to the instrument cluster by the ABS/TC module over the SCP communication network.

Tachometer Gauge

The instrument cluster uses crankshaft speed information, sent to the PCM from the crankshaft position sensor, to control the movement of the tachometer pointer. The crankshaft position sensor is hardwired directly to the PCM, which provides the crankshaft position sensor status to the instrument cluster over the SCP communication network.

Temperature Gauge

The cylinder head temperature sending unit is hardwired directly to the PCM. The status of the cylinder head temperature is sent from the PCM over the SCP communication network to the instrument cluster. Normal operating temperature is 60° C (140° F) to 120° C (248° F). Redline starts at 121° C (249.8° F).

Warning Indicator Lamps

Air Bag Warning Indicator

The supplemental restraint system is monitored and controlled by the RCM. The status of the supplemental system is sent from the RCM to the instrument cluster through hardwired circuitry. The AIR BAG warning indicator is illuminated when the RCM removes the ground signal to the instrument cluster.

Anti-Lock Brake System (ABS) Warning Indicator

The ABS is monitored by the ABS or ABS/TC module, which sends the status signal to the instrument cluster over the SCP communication network. The instrument cluster uses this input to determine whether or not there is a fault with the ABS or ABS/TC system and turns on the ABS warning indicator according to the input.

Brake Warning Indication

The BRAKE warning indicator illuminates when either the parking brake is engaged, the brake fluid level is low or a base brakes system concern exists. These functions are controlled by the electronic parking brake module, the brake fluid level switch and the ABS system module. The electronic parking brake module monitors the Driver input through the switch and sends an SCP message to the instrument cluster when the parking brake has been selected ON. The brake fluid level switch is hardwired directly to the FEM. when the brake fluid is low, the FEM sends a signal to the instrument cluster over the SCP communication network to turn on the brake warning indicator. The ABS module monitors the base brake system and sends an SCP message to the instrument cluster if a concern exists to turn on the BRAKE warning indicator.

Charging System Warning Indicator

The charging system controls are accomplished through the PCM, which monitors the output of the generator through hardwired circuitry. The status of the charging system is then relayed from the PCM to the instrument cluster over the SCP communication network.

Door Ajar Warning Indicator

The instrument cluster uses door ajar status provided by the FEM over the SCP communication network.

The door switches are directly hardwired to the FEM, which uses the multiple inputs from each door switch to determine whether the doors are in the opened or closed position and relays the status to the instrument cluster to turn on or oft the door ajar indicator.

Engine Over-Temperature Warning Indicator

The engine over-temperature status is determined by the cylinder head temperature sender unit, which is hardwired directly to the PCM. The status of the cylinder head temperature is sent from the PCM over the SCP communication network to the instrument cluster.

Low Fuel Warning Indicator

There are two fuel tank senders, which are hardwired directly to the REM. The status of the fuel level from both senders is sent from the REM over the SCP communication network to the instrument cluster. The instrument cluster uses these inputs to determine the overall fuel level in the tank and illuminates the low fuel warning indicator if the fuel level is low.

Low Washer Fluid Warning Indicator

The washer fluid switch is hardwired directly to the FEM. The FEM monitors the washer fluid level status and sends it to the instrument cluster over the SCP communication network to turn on or oft the low washer fluid warning indicator.

Safety Belt Warning Indicator

Safety belt warning indication is accomplished through the safety belt switch, which is hardwired directly to the instrument cluster. The instrument cluster uses the ground or open input from the switch to determine whether or not the safety belt is fastened. When the safety belt is fastened, the safety belt switch opens and removes the ground to the instrument cluster. when the safety belt is unfastened, the safety belt switch closes and grounds the circuit to the instrument cluster.

Indicator Lamps

CHECK FUEL CAP

The CHECK FUEL CAP indicator is used to indicate significant leaks in the fuel tank evaporative system due to a loose fuel cap. Fuel tank pressure is monitored by the PCM and if a leak is detected it signals a fault to the instrument cluster over the SCP network. Once the PCM has detected a loose fuel cap and the CHECK FUEL CAP indicator is illuminated, the indicator will remain illuminated until the fuel cap is secured and the ignition switch has been cycled one time.

Electronic Throttle Control Indicator

The PCM monitors the electronic throttle control and provides the instrument cluster with the electronic throttle control status over the SCP communication network. When a system concern is detected, the PCM provides the instrument cluster with a signal commanding the instrument cluster to turn on the electronic throttle control lamp.

High Beam Indicator

The multifunction switch is hardwired directly to the instrument cluster. The headlamp status is then sent from the instrument cluster to the FEM over the SCP communication network.

Low Oil Pressure Indicator

The engine oil pressure switch is hardwired to the FEM, which monitors the oil pressure status. The oil pressure status is then sent from the FEM to the instrument cluster over the SCP communication network to turn on or off the low oil pressure indicator.

Malfunction Indicator Lamp (MIL)

After the engine is started, the MIL proves out for a duration of three seconds. If the instrument cluster does not receive a message from the PCM within five seconds, it sends two messages to the PCM and attempt to re-establish communication. If the instrument cluster is unable to re-establish communication, the instrument cluster will illuminate the MIL and log a diagnostic trouble code (DTC).

Speed Control Indicator

The speed control status is monitored by the PCM and then relayed to the instrument cluster over the SCP communication network. The speed control indicator illuminates when the speed control is set.

Traction Control Indicator

The status of the traction control is communicated to the instrument cluster from the ABS/TC module via the SCP communication network. when the traction control system is active, the ABS/TC module sends a command to the instrument cluster to illuminate the traction control indicator.

Turn/Hazard Indicator

The multifunction switch is hardwired directly to the instrument cluster. The instrument cluster sends the signal from the multifunction switch to both the FEM and REM over the SCP communication network while simultaneously illuminating the turn/hazard indicators. The FEM and the REM use these inputs from the instrument cluster to illuminate the exterior lighting as necessary.
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