Principles of Operation

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

NOTE: Whenever a network message is suspected as missing and confirmed by a missing message DTC (U-code), 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 IC, it may be helpful to review the complete message list available in MODULE COMMUNICATIONS NETWORK article 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) utilizes a microprocessor to control the gauge, indicator, message center and warning chime functions. Data is sent to the instrument cluster (IC) over the high speed controller area network (HS-CAN), the medium speed controller area network (MS-CAN) bus lines and through hardwired circuitry from individual components. The instrument cluster (IC) uses each input to output an action to the gauges or indicators.

It is very important to understand:

where the input originates.
all the information 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 control the output of the feature, or does it output a message over the communication network to another module.
which module controls the output of the feature.

Instrument Cluster (IC)

Instrument Cluster (IC) Gateway Function

The instrument cluster (IC) acts as a gateway module by receiving information in one format and transmitting it to other modules using another format. For example, the instrument cluster (IC) receives the vehicle speed data from the PCM over the HS-CAN, converts the data into a MS-CAN message and sends (gateways) the message to other network modules such as the HVAC module, the tire pressure monitoring system (TPMS), the parking aid module (PAM), and the SJB. This enables network communication between modules that do not communicate using the same network (HS-CAN or the MS-CAN).

Instrument Cluster (IC) Network Messages

The instrument cluster (IC) uses input messages from other modules to control the gauges, informational indicators, and warning indicators 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 O/D off status message is missing for less than 5 seconds and the O/D off indicator was on (O/D cancelled), the indicator remains in the on state until the next good message is received. If the message remains missing or invalid for more 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 the normal operation descriptions located before each individual pinpoint test for a further description 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.

NOTE: Whenever a network message is suspected as missing and confirmed by a missing message DTC (U-code), 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 MODULE COMMUNICATIONS NETWORK article 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.

Instrument Cluster (IC) Configuration

The instrument cluster (IC) contains items that are configurable. While some configurable items are customer preference items, most items are configured at the end of the line production and only available for configuration using As-Built data. Refer to MODULE CONFIGURATION article for module configuration information. The overspeed chime enabled and the Belt-Minder® feature are the only customer preference configurable items in the instrument cluster (IC).

NOTE: When installing a new instrument cluster (IC), it is necessary to upload the module configuration to the scan tool. Following installation of the instrument cluster (IC), download the module configuration from the scan tool into the new instrument cluster (IC). Refer to MODULE CONFIGURATION article. It is also necessary to carry out a parameter reset procedure whenever a new instrument cluster (IC) or PCM is installed. Refer to ANTI-THEFT - PASSIVE ANTI-THEFT SYSTEM (PATS) article.

Transit Mode

The transit mode is used to prevent the instrument cluster (IC) from draining the vehicle battery when the vehicle is unused for an extended period of time (possibly while parked in a dealer lot or the assembly plant waiting on transportation from the plant to the dealer). The transit mode conserves the battery reserve voltage by shortening the delayed accessory window of operation. The instrument cluster (IC) is designed to automatically restore full delayed accessory operation between 79-80 km (49-50 miles).

Instrument Cluster (IC) Prove-Out

The instrument cluster (IC) and other vehicle modules carry out a display prove-out to verify that all module controlled warning/indicator lamps and monitored systems are functioning correctly within the instrument cluster (IC). The instrument cluster (IC) and other modules, such as the restraints control module (RCM), provide a timed prove-out while other indicators illuminate until engine start up. When the ignition switch is cycled to the ON position with the engine off, the indicators illuminate to prove-out according to the following table:

Indicator	Indicator Type	Prove-Out Duration
Air bag	Warning	6 seconds
ABS	Warning	3 seconds
Anti-theft	Indicator	Approximately 2 seconds (if the system is operating correctly)
Brake	Warning	3 seconds
Charging system	Warning	Until engine startup
Check fuel cap indicator	Informational	3 seconds
Door ajar warning indicator	Warning	None
High beam indicator	Informational	None
Low fuel indicator	Informational	None
Low oil pressure warning indicator	Warning	Until engine startup
Low washer fluid indicator	Informational	3 seconds
Malfunction indicator lamp (MIL)	Warning	Until engine startup
Overdrive off indicator	Informational	None
Safety belt warning indicator	Warning	70 seconds if the safety belt is unbuckled, turns off when the safety belt is buckled
Speed control indicator	Informational	None
Tire pressure monitoring system (TPMS) warning indicator	Warning	3 seconds
Traction control indicator	Warning	3 seconds
Powertrain malfunction (wrench) indicator	Warning	3 seconds
RH/LH turn indicators	Informational	None

Integrated Circuit Display

The integrated circuit display contains the odometer, trip odometer, and compass display on base clusters and the message center display on message center clusters. The compass module (part of the interior rear view mirror) is hardwired to the instrument cluster (IC). The odometer information is transmitted from the PCM over the communication network to the instrument cluster (IC). The instrument cluster (IC) displays the appropriate message(s) upon receipt of the compass heading and odometer data received.

Information And Message Center

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, indicators, and warning indicators. The message center, located in the center of the instrument cluster (IC) is a vacuum fluorescent 2-line display. 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.

Warning Chimes

Warning Chime Characteristics

Each warning chime has unique characteristics that help to identify and differentiate each warning chime. The warning chimes use volume, chime frequency, length of time the chime sounds and the number of chime tones to identify which chime is sounding. The instrument cluster (IC) prioritizes the chimes according to a preset hierarchy programmed into the instrument cluster (IC) software. When more than one chime request is received by the instrument cluster (IC), the most important chime sounds. If a lower priority chime is currently sounding, the higher priority request takes over and replaces the lower priority chime.

There are 2 basic chime types:

Repetitive
Single tone

The following table provides a summary of the chime characteristics including the chime priority.

INSTRUMENT CLUSTER (IC) CHIME CHARACTERISTICS

Chime Name	Number of Chime Tones	Condition/Description
Safety belt	6 one-second duration tones.	On for as long as the safety belt is unbuckled and the instrument cluster (IC) receives the chime on command.
Air bag	5 one-second duration tones.	Consists of 5 sets of chimes that make up a chime cycle. Each chime set is 5 one-second on/one-second off chimes followed by a 5-second delay. There is a 30 minute delay between each cycle of chime sets.
Key-in-ignition	Repetitive, 0.5-second duration tones.	On for as long as the instrument cluster (IC) receives the chime on command (the key is in the ignition, the ignition switch is in the OFF or ACC position and the is door ajar).
Turn signal left on	Repetitive, 0.37-second duration tones.	On for as long as the RH or LH turn signal is on and the instrument cluster (IC) receives the chime on command once the vehicle has driven for 3.2 km (2.0 miles).
Door ajar	Single one-second duration tone.	This is a single tone chime that sounds when the key is in the RUN position and a door changes from closed to ajar.
Headlamps on	Repetitive, 0.25-second duration tones.	On for as long as the instrument cluster (IC) receives the chime on command (headlamps on, LH front door ajar and the ignition switch in the OFF or ACC positions).
Message center (if equipped)	Single one-second duration tone.	This is a single tone chime that sounds once per warning whenever the instrument cluster (IC) receives a new message commanding on the low brake fluid level, tire pressure monitoring system (TPMS), low fuel level or check brake system message center warnings.
Parking brake on	Repetitive, 90 one-second duration tones.	On for as long as the parking brake is applied and the instrument cluster (IC) receives the chime on command.
Belt-Minder® A/B	Belt-Minder® A: 6 one-second sequences of 0.5-second on/0.5-second off. Belt-Minder® B: 6 one-second sequences of 0.2-second on/0.2-second off then 0.3-second on/0.3-second off.	On for as long as the instrument cluster (IC) receives the Belt-Minder® chime request.

Safety Belt Warning Chime

The safety belt warning chime warns that the safety belt is not fastened. The safety belt warning chime sounds when the driver or passenger safety belt is not fastened and the ignition lock cylinder is turned from the OFF/LOCK or ACC to the ON or START position.

The safety belt warning chime stops sounding when the safety belt is fastened, when the ignition switch is turned from the ON or START position to the OFF/LOCK or ACC position, or when the chime has sounded for approximately 6 seconds.

The safety belt warning chime inputs are:

Ignition switch RUN/START status.
Driver or passenger safety belt switch data communicated by the restraints control module (RCM) to the instrument cluster (IC) through the high speed controller area network (HS-CAN).

Belt-Minder®

The Belt-Minder® is configurable. Refer to MODULE CONFIGURATION article. To configure without using a scan tool, refer to Belt-Minder® Deactivating/Activating .

The Belt-Minder® feature supplements the current safety belt warning function and is enabled after the current safety belt warning is complete. The Belt-Minder® reminds the driver that the driver or passenger safety belt is unbuckled by intermittently sounding a chime and illuminating the safety belt warning lamp in the instrument cluster (IC) once the vehicle speed has exceeded 5 km/h (3 mph), and remains active for 5 minutes from the time it is started. While activated, the Belt-Minder® chime and indicator flash and chime simultaneously from on for 6 seconds to off for 30 seconds.

NOTE: The Belt-Minder® is disabled for one ignition switch on cycle if the safety belt is buckled then unbuckled within 20 seconds during that specific cycle.

The Belt-Minder® warning chime inputs are the:

Ignition switch RUN/START status
Driver or passenger safety belt switch data communicated by the RCM to the instrument cluster (IC) through the HS-CAN.

Key-In-Ignition Warning Chime

The key-in-ignition warning chime warns that the key is still in the ignition lock cylinder when the driver door is ajar. The key-in-ignition warning chime sounds when the driver door is ajar, the key is in the ignition lock cylinder and in the OFF/LOCK or ACC position.

The key-in-ignition warning chime stops sounding when the driver door is closed, the key is removed from the ignition lock cylinder, or if the ignition switch is turned to the ON position.

The key-in-ignition warning chime inputs are:

Ignition switch RUN/START status.
Key-in-ignition switch position to the SJB.
Door ajar input from the driver door ajar switch to the SJB.
Key-in-ignition chime request communicated by the SJB to the instrument cluster (IC) through the medium speed controller area network (MS-CAN).

Headlamps On Warning Chime

The headlamps on warning chime warns that the headlamps are on when the driver door is ajar and the key is removed from the ignition lock cylinder. The headlamps on warning chime sounds if the driver door is ajar, the headlamp switch is in the PARK or HEADLAMP position, and the ignition switch is in the OFF/LOCK position with the key removed.

The headlamps on warning chime stops sounding when any one of the above conditions are removed.

The headlamps on warning chime inputs are:

Ignition switch position to the SJB.
Key-in-ignition switch position to the SJB.
Door ajar input from the driver door ajar switch to the SJB.
Headlamp switch input to the SJB.
Headlamps on chime request communicated by the SJB to the instrument cluster (IC) through the MS-CAN.

Door Ajar Warning Chime

The door ajar warning chime warns that a door is open or not fully closed. The chime sounds when any door, or the liftgate becomes ajar while the ignition switch is in the ON position.

The door ajar warning chime stops sounding and resets when all the doors and the luggage compartment lid are closed, or the ignition lock cylinder is placed in the OFF/LOCK or ACC position.

The door ajar warning lamp/chime inputs are:

Ignition switch RUN/START status.
Door ajar data communicated by the SJB to the instrument cluster (IC) through the MS-CAN.

Turn Signal On Warning Chime

The turn signal on warning chime warns that the turn signal has not been cancelled. The turn signal on warning chime sounds if the left or right turn signal is on and the vehicle has traveled more than 3.2 km (2.0 miles).

The turn signal on warning chime stops sounding if the turn signal is turned off, or if the ignition lock cylinder is turned to the OFF or ACC position.

The turn signal on warning chime inputs are:

Turn signal on data communicated by the SJB to the instrument cluster (IC) through the CAN communication.
Odometer count data communicated by the PCM to the instrument cluster (IC) through the HS-CAN.

Parking Brake Warning Chime

The parking brake warning chime warns that the parking brake is engaged when the vehicle is in motion. The parking brake warning chime sounds if the ignition switch is in ON position, the parking brake is engaged, and the vehicle speed is greater than 5 km/h (3 mph).

The parking brake warning chime stops sounding and resets if the parking brake is released, the ignition switch is not in the ON position, if the vehicle speed is less than 5 km/h (3 mph), or after 90 seconds from the time the chime is activated.

The parking brake warning chime inputs are:

Ignition switch RUN/START status.
Parking brake switch status communicated by the SJB to the instrument cluster (IC) through the MS-CAN.
Vehicle speed data communicated by the PCM to the instrument cluster (IC) through the HS-CAN.

Air Bag Secondary Warning Chime

The air bag secondary warning chime warns that the air bag warning indicator light does not work correctly. The instrument cluster (IC) monitors the air bag warning indicator status internally. When a fault is present in the air bag warning indicator and the instrument cluster (IC) receives an air bag warning indicator on request from the RCM, the air bag secondary warning chime sounds.

The air bag secondary warning chime inputs are:

Ignition switch RUN/START status.
Air bag warning indicator request data is communicated by the RCM to the instrument cluster (IC).

Turn/Hazard On Tone

Since the turn and hazard flasher is an electronic function of the SJB, the on/off sound that used to be present with standard bi-metal flashers is no longer present. To provide an audible sound and indicate that the RH/LH turn or hazard indicators are on, the instrument cluster (IC) provides an tic-toc tone along with the visual turn signal indicators.

The turn/hazard on tone inputs are:

Left turn indicator signal from the SJB to the instrument cluster (IC) through the MS-CAN.
Right turn indicator signal from the SJB to the instrument cluster (IC) through the MS-CAN.