Principles of Operation (How Does It Work)

NOTE:
^ The Instrument Cluster (IC), Front Electronic Module (FEM), and the Rear Electronic Module (REM) must be reconfigured upon replacement. Refer to Module Communications Network (Information Bus).
^ For any concerns with the Restraint Control Module (RCM), refer to Air Bag Systems.

The IC is a hybrid electronic instrument cluster. The vehicle electronic functions are divided into zones. The IC, FEM, and REM use the Standard Corporate Protocol (SCP) communication network to transmit and receive information. As a technician 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
^ does the module which received the input (message), control the output of the feature, or does it output a message over the SCP communication network to another module
^ which module controls the output of the feature

The IC communicates with the FEM, REM, Anti-Lock Brake System/Traction Control/Interactive Vehicle Dynamics (ABS/TC/IVD), Powertrain Control Module (PCM), Steering Column Lock (SCL), Message Center module, and the Restraint Control Module over the SCP to control the gauges, indicators, and chimes.

Warning Indicator Functionality

Low Oil Pressure Indication
The low oil pressure switch is hardwired to the FEM. The status of the oil pressure is sent from the FEM to the instrument cluster via the SCP communication network.

Safety Belt Warning Indication
The safety belt switch is hardwired directly to the IC. The IC uses the input from the switch to determine whether or not the safety belt is fastened.

Door Ajar Warning Indication (If equipped)
The door switches for the rear of the vehicle are directly hardwired to the REM. The REM uses the multiple inputs from the door switches to determine whether the doors are in the opened or closed position. This information is then relayed from the REM to the instrument cluster via the SCP communication network. The door switches for the front of the vehicle are directly hardwired to the FEM. The FEM uses the multiple inputs from the door switches to determine whether the doors are in the opened or closed position. This information is then relayed to the instrument cluster via the SCP communication network.

Charging System Warning Indication
The charging system is hardwired to the PCM. The status of the charging system is then relayed from the PCM to the instrument cluster via the SCP communication network.

Brake Warning Indication
The brake warning indicator supports three separate functions. Those functions are brake system failure, low brake fluid level, and engagement of the parking brake control. These functions are controlled by the parking brake control switch, the brake fluid level switch and the brake system itself. The brake fluid level switch and the parking brake control switch are hardwired directly to the FEM. The status of both the fluid and parking brake control switches is sent from the FEM to the instrument cluster via the SCP communication network. The brake system status is sent from the ABS/TC/IVD to the instrument cluster via the SCP communication network.

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

Low Washer Fluid Warning Indication (If equipped)
The low washer fluid level switch is hardwired directly to the FEM. The FEM monitors the washer fluid level status and sends it to the instrument cluster via the SCP communication network.

Air Bag Warning Indication
The AIR BAG warning indicator will be illuminated when the Electronic Crash Sensor (ECS) sends a ground signal to the instrument cluster. The prove out of the AIR BAG warning indicator is controlled by the ECS.

ABS Warning Indication
The status of the ABS/TC/IVD system is sent to the instrument cluster via the SCP communication network. The instrument cluster uses this input to determine whether or not there is a fault with the ABS/TC/IVD system.

Traction Control Warning Indication
The status of the traction control is communicated to the instrument cluster from the TC/IVD module via the SCP communication network.

Advance Traction Warning Indication
The status of the system is communicated to the instrument cluster from the IVD module via the SCP communication network.

Lamp Outage Warning Indication (If equipped)
The FEM and REM both control the exterior illumination. If the exterior lamps are the cause of the fault, these two modules will notify the instrument cluster via the SCP communication network and cause the lamp outage warning indicator to illuminate.

Malfunction Indicator Lamp (MIL)
After the engine is started, the MIL will prove out for a duration of three seconds. If the instrument cluster does not receive a message from the PCM within five seconds, it will send two messages to the PCM and attempt to reestablish communication. If the instrument cluster is unable to reestablish communication, the instrument cluster will illuminate the MIL and log a Diagnostic Trouble Code (DTC).

Turn/Hazard Indication
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 via 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.

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

Low Fuel Warning Indication (If equipped)
There are two fuel tank senders, and they 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.

Engine Over-Temperature Indicator
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. The instrument cluster then determines whether or not the cylinder head temperature is above the over-temperature threshold.

Steering Column Lock Indication
The SCL status is monitored by the instrument cluster from the input of the SCL module via the SCP communication network.

Gauge Functionality

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 140° F (60° C) to 248° F (120° C). Redline starts at 249.8° F (121° C).

Tachometer Gauge
The crankshaft position sensor is hardwired directly to the PCM. The status of the crankshaft position sensor is sent from the PCM to the instrument cluster via the SCP communication network.

Speedometer Gauge
The vehicle speed signal (VSS) from all four wheels are hardwired directly to the ABS/TC/IVD. The speed status is then sent to the instrument cluster by the ABS/TC/IVD via the SCP communication network.

Fuel Gauge
The fuel gauge system has a saddle-type fuel tank with two integrated fuel senders: the Fuel Delivery Module (FDM) and the Jet Pump Module (JPM). The FDM is located in the right side of the fuel tank and the JPM 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 FDM is from 16 ± 2 ohms at empty (E) to 155 ± 4 ohms at full (F). Normal operating range of the JPM sender is from 19 ± 2 ohms at empty (E) to 160 ± 2 ohms at full (F). If either the REM or JPM fuel sender has an open or shorted signal, the instrument cluster will log DTC B1201. If the JPM sender is open, the fuel gauge will default to the FDM sender value only and the fuel gauge will indicate E to 1/2 tank (depending on the fuel level on the FDM side of the tank). If the FDM is open, the fuel gauge will default to the empty position.

Digital Segment Displays

Trip A/B And Odometer Displays
The VSS from all four wheels are hardwired directly to the ABS/TC/IVD. The speed status is then sent to the instrument cluster by the ABS/TC/IVD via the SCP communication network to establish a rolling count.

PRNDL Display
The digital transmission range sensor is hardwired directly to the PCM. The status of the gear selection is sent to the instrument cluster from the PCM via the SCP communication network.

Parameter Reset and Programming Keys

NOTE:
^ The Instrument Cluster Module (ICM) parameters must be reset upon installation of a new ICM.
^ Both Passive Anti-theft System (PATS) keys are needed to carry out this procedure.

To reset the ICM parameters and programming keys, complete the following procedure:
1. Connect the scan tool.
2. Select PCM.
3. Select ENTER SECURITY ACCESS. Wait 10 minutes for security access to be granted.
4. Select PARAMETER RESET.
5. Select ICM.
6. Select ENTER SECURITY ACCESS. Wait 10 minutes for security access to be granted.
7. Select PARAMETER RESET.
8. Disconnect the scan tool.
9. Place ignition key in the OFF position.
10. Place ignition key in the RUN position.
11. Remove the ignition key.
12. Place the second PATS key in the RUN position.
13. Place the ignition key in the OFF position.