Principles of Operation

PRINCIPLES OF OPERATION

NOTE: The smart junction box (SJB) is also known as the generic electronic module (GEM).

The message center information can be selected through the SELECT/RESET button (base cluster) and by the INFO, SETUP, and RESET buttons (high series cluster).

The message center is an integral part of the instrument cluster (IC) that receives and acts upon much of the same information that is input and used to operate the instrument cluster (IC) gauges, informational indicators, and warning indicators. The message center, located in the center of the instrument cluster (IC) is a liquid crystal display (LCD). The message center electronic functions use both hardwired and the controller area network (CAN) circuitry to transmit and receive information.

Whenever conditions are present that require a warning message, the message center replaces the last selected display with the new warning display. Once the message is reset or cleared, the message center returns to the last selected display. If multiple warnings are present, the message center displays each warning for approximately 4 seconds. Warning messages are also generally associated with other observable instrument cluster (IC) indications. For example, when the LH front door is opened, the message center displays the message DRIVER DOOR AJAR along with the door ajar warning indicator. This allows the message center to be a more informative supplement to the instrument cluster (IC) gauges and indicators.

It is very important to understand:
- where the input (command) originates.
- all the information (messages) necessary in order for a feature to operate.
- which module(s) receive(s) the input or command message.
- if the module that received the input (message) controls the output of the feature, or if it outputs a message over the CAN to another module.
- which module controls the output of the feature.

Instrument Cluster (IC) Network Messages

NOTE: Whenever a network message is suspected as missing, confirmed by a missing message DTC, it is important to look for other symptoms that may also be present in the instrument cluster (IC) and throughout the vehicle. Once a DTC is set in the instrument cluster (IC), it may be helpful to review the complete message list available in Information Bus (Module Communications Network) to see what other modules also rely on the same message and run the self-test for those modules. If the message is missing from other modules, the same DTC may also be set in those modules. Confirmation of missing messages common to multiple modules may indicate that the originating module is the source of the concern or the communication network may be experiencing some problems.

The instrument cluster (IC) uses input messages from other modules to control the gauges, informational indicators, warning indicators and message center displays over the communication networks. If a required message is missing or invalid for less than 5 seconds, the gauge or indicator that requires the message remains at the last commanded state based upon the last known good message. For example, if the message is missing for the driver door ajar off status for less than 5 seconds and the door ajar indicator was on, the indicator remains in the on state until the next good message is received. If the message remains missing or invalid for greater than 5 seconds, the instrument cluster (IC) sets a U-code DTC and the output becomes a default action for the indicator or gauge. Each indicator or gauge utilizes a different default strategy depending on the nature of the indication. Refer to Instrument Cluster for further descriptions of the default action specific to each indicator or gauge. If the messaged input to the cluster returns at any time, the normal function of the gauge or indicator resumes.

Message Center Features
The message center provides the following features:
- Information displays
- Setup displays
- System check messages
- Warning messages

Information Displays (Base Instrument Cluster [IC])
The information displays are non-timed modes. The selected mode remains on until the driver presses the SELECT/RESET switch to change the mode, or until it is overridden by another mode. The information display modes are:
- Odometer/trip odometer, compass headings
- Outside air temperature display (if equipped)
- Distance to empty
- Average fuel economy
- Setup menu

Information Displays (High Series Instrument Cluster [IC])
The information displays are non-timed modes. The selected mode remains on until the driver presses a message center switch to change the mode, or until it is overridden by another mode. The information display modes are:
- Odometer/trip odometer, compass headings, outside air temperature display
- Distance to empty
- Average fuel economy
- Instantaneous fuel economy
- Fuel used
- Trip elapsed drive time
- Blank

Setup Displays (Base Instrument Cluster [IC])
The setup displays are timed modes and terminate after a finite interval. Press the SELECT/RESET button to scroll through the SETUP MENU display sequence. If the SELECT/RESET button is not pressed within 4 seconds, the message center returns to the INFO MENU. The setup display modes are:
- System check
- Units (English/metric)
- Language
- Autolamp
- Autolock
- Auto-unlock
- Parking aid (if equipped)
- Oil life reset and start value

Setup Displays (High Series Instrument Cluster [IC])
The setup displays are timed modes and terminate after a finite interval. Press the SETUP button for the following displays:
- System check
- Units (English/metric)
- Language
- Autolamp
- Autolock
- Auto-unlock
- Running boards (if equipped)
- Easy entry/exit seat (if equipped)
- Parking aid (if equipped)
- Compass zone
- Compass calibration
- Oil life reset and start value

System Check Displays
Selecting this function from the SETUP MENU causes the message center to cycle through each of the systems being monitored. For each of the monitored systems, the message center indicates either an OK message or a warning message for 2 seconds. For base instrument clusters (IC), the SELECT/RESET button must be held down after pressing the SELECT/RESET button to cycle the messages through each of the systems being monitored. For high series instrument clusters (IC), pressing the RESET control switch cycles the message center through each of the systems being monitored. The system check report is as follows:
- OIL LIFE
- CHARGING SYSTEM
- WASHER FLUID
- DOOR AJAR
- EXTERIOR LAMPS
- BRAKE FLUID LEVEL
- PARK BRAKE
- FUEL LEVEL AND DISTANCE TO EMPTY (high series instrument cluster [IC])
- MILES TO EMPTY (base instrument cluster [IC])
- FUEL LEVEL LOW (base instrument cluster [IC])

System Warnings
The system warnings alert the operator to possible problems or malfunctions in the vehicle operating systems. The message center displays the last selected feature if there are no more warning messages. This allows the operator full functionality of the message center after acknowledgement of the warning message by pressing the reset button and clearing the message. The warning messages are divided into 4 categories:
- They cannot be cleared until the condition is corrected.
- They reappear on the display 10 minutes from the reset if the condition has not been corrected.
- They do not reappear until an ignition OFF-ON cycle has been completed.
- They reappear if the condition clears then reoccurs within the same ignition ON-OFF cycle.

The warning displays that cannot be reset are:
- DOOR AJAR

The warning messages that reoccur after 10 minutes are:
- FUEL LEVEL LOW
- PARK BRAKE ENGAGED
- CHECK BRAKE SYSTEM

The warning messages that display whenever the ignition switch is turned from the OFF position to the ON position are:
- CHECK PARK AID (if equipped)
- BRAKE FLUID LEVEL LOW
- CHECK HEADLAMP
- CHECK HIGHBEAM
- CHECK TURN LAMP
- WASHER FLUID LOW LEVEL
- OIL CHANGE REQUIRED
- ENGINE OIL CHANGE SOON

The warning messages that return after a condition has cleared then reoccurs within the same ignition ON-OFF cycle are:
- LIFTGATE/GLASS AJAR
- CLEAR OBJECTS BY PASS SEAT
- CHECK CHARGING SYSTEM
- LOW TIRE PRESSURE
- TIRE MONITOR FAULT
- TIRE SENSOR FAULT

The message center displays messages that indicate a system state during the operation of the four wheel drive (4WD) system. The displayed warning messages are as follows:
- FOR 4X4 LOW STOP VEHICLE (if equipped)
- FOR 4X4 LOW SHIFT TO N (if equipped)
- TO EXIT 4X4 LOW STOP VEHICLE (if equipped)
- TO EXIT 4X4 LOW SHIFT TO N (if equipped)

The message center displays messages that indicate a system state during repair procedures related to the tire pressure monitoring system (TPMS). The displayed warning messages are as follows:
- TRAIN TIRES
- TIRES TRAINED
- TIRES NOT TRAINED

The message center displays messages that indicate a system state during repair procedures related to the compass display. The displayed warning messages are as follows:
- COMPASS ZONE XX (base instrument cluster [IC])
- RESET FOR ZONE SETTING (high series instrument cluster [IC])
- ZONE XX RESET TO CHANGE (high series instrument cluster [IC])
- ZONE XX IS SET
- PRESS RESET FOR CALIBRATION (high series instrument cluster [IC])
- CIRCLE SLOW TO CALIBRATE (base instrument cluster [IC])
- CIRCLE SLOWLY TO CALIBRATE (high series instrument cluster [IC])
- CALIBRATION COMPLETED

The message center displays messages that indicate a system state during repair procedures related to the oil life and oil life start value. The displayed warning messages are as follows:
- HOLD RESET IF NEW OIL
- OIL LIFE SET TO 100%
- OIL LIFE START VALUE SET TO XXX% (high series instrument cluster [IC])
- OIL LIFE SET TO XXX% (base instrument cluster [IC])

Outside Air Temperature Sensor (Instrument Cluster [IC] Without Electronic Automatic Temperature Control [EATC])
The instrument cluster (IC) receives the outside air temperature data from the outside air temperature sensor. This data is then displayed on the message center. The outside air temperature sensor is located on the radiator core support behind the front grill assembly and is fastened with a pin-type retainer. If equipped with EATC, the outside air temperature data from the outside air temperature sensor is displayed in the heating ventilation air conditioning (HVAC) module. Refer to Heating and Air Conditioning for the outside air temperature display in the EATC.

Compass
The compass heading is displayed as one of N, NE, E, SE, S, SW, W and NW in the message center display. The compass reading may be affected when you drive near large buildings, bridges, power lines and powerful broadcast antenna. Magnetic or metallic objects placed in, on or near the vehicle may also affect compass accuracy. The compass sensor module is mounted behind the interior rear view mirror.