Principles Of Operation
Instrumentation, Message Center and Warning Chimes
Principles of Operation
NOTE: The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).
The Instrument Cluster (IC) utilizes a microprocessor to control the gauge, indicator, message center and warning chime functions. Data is sent to the IC over the High Speed Controller Area Network (HS-CAN) and Medium Speed Controller Area Network (MS-CAN) bus lines and through hardwired circuitry from individual components. The 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)
IC Gateway Function
The IC acts as a gateway module by receiving information in one format and transmitting it to other modules using another format. For example, the IC receives the vehicle speed data from the PCM over the High Speed Controller Area Network (HS-CAN), converts the data into a Medium Speed Controller Area Network (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.
IC Network Messages
The IC uses input messages from other modules to control the gauges, informational indicators, warning indicators and message center 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 Overdrive (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 greater than 5 seconds, the 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 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 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 Description and Operation 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.
IC Configuration
The IC contains items that are configurable. Configurable items include customer preference items, which can also be set with a scan tool. The remaining configurable items can be set only through the Programmable Module Installation (PMI) procedure or by using As-Built data. Refer to Module Configuration Programmable Module Installation (PMI).
NOTE: When installing a new IC, it is necessary to upload the module configuration to the scan tool. Following installation of the IC, download the module configuration from the scan tool into the new IC. Refer to Module Configuration Programmable Module Installation (PMI) to carry out PMI. It is also necessary to carry out a parameter reset procedure whenever a new IC or PCM is installed. Passive Anti-Theft System (PATS) Parameter Reset
IC Configuration Parameters
IC Prove-Out
The 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 IC. When the ignition switch is cycled to the ON position with the engine off, the indicators illuminate to prove-out according the following table:
Information And Message Center
The message center is an integral part of the IC that receives and acts upon much of the same information that is input and used to operate the IC gauges, indicators, warning indicators and message center indicators. The message center, located in the center of the IC is a 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 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 message center indicator. This allows the message center to be a more informative supplement to the IC gauges and indicators.
Warning Chimes
The IC uses inputs that are both hardwired to individual components and messages that are sent from the other modules over the HS-CAN or MS-CAN to control the warning chime functions.
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 IC prioritizes the chimes according to a preset hierarchy programmed into the IC software. When more than one chime request is received by the 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 3 different chimes as listed below:
- Repetitive
- Single tone
- tick-tock
The following table provides a summary of the chime characteristics including the chime priority.
IC Chime Characteristics/Priority
Air Bag Warning Chime
The air bag warning chime warns that a fault is present within the air bag warning indicator circuit. The Restraints Control Module (RCM) provides the air bag warning indicator message to the IC. The IC monitors the internal air bag warning indicator circuitry and turns on the air bag warning chime if a fault is present.
The air bag warning chime input is the air bag warning indicator request from the RCM.
Belt-Minder(R) Warning Chime
The safety Belt-Minder(R) feature is configurable. Refer to Module Configuration [1][2]Initial Inspection and Diagnostic Overview. To configure without using a scan tool, refer to Belt-Minder(R) Deactivating/Activating Service and Repair.
The Belt-Minder(R) feature is controlled by a message sent to the IC from the RCM and supplements the safety belt warning chime and safety belt warning indicator functions. The Belt-Minder(R) reminds the driver that the safety belt is unbuckled by intermittently sounding a chime and illuminating the safety belt warning lamp in the IC. The Belt-Minder(R) feature is enabled after the safety belt warning chime is complete and the vehicle speed has exceeded 4.8 km/h (3 mph). While activated, the Belt-Minder(R) alternates the chime and safety belt warning indicator from ON for 6 seconds to OFF for 30 seconds then the sequence repeats. If the Belt-Minder(R) remains active after 3 repetitions, the sound level and the speed of the chimes increase.
When a MyKey(TM) is in use, the driver cannot configure the Belt-Minder(R) off. Once the Belt-Minder(R) is activated, the Belt-Minder(R) continues to chime periodically (does not time out after 5 minutes) and the audio system is muted until the driver and passenger safety belts are fastened. Refer to Anti-Theft - Passive Anti-Theft System (PATS) Anti-Theft - Passive Anti-Theft System (PATS) for more information on the MyKey(TM) feature.
The Belt-Minder(R) warning chime inputs are the:
- Ignition switch RUN/START position
- Ignition switch RUN/ACC position
- Driver safety belt switch message from the RCM
The Belt-Minder(R) reminder stops when:
- The driver safety belt is buckled
- The ignition switch is turned to the OFF or ACC position
Door Ajar Warning Chime
The door ajar warning chime warns that a door is ajar. The door ajar warning chime is a single chime with a 1 second duration. The door ajar chime sounds when the driver or passenger door, liftgate or liftgate glass becomes ajar while the ignition switch is in the RUN position.
The door ajar warning chime inputs are the:
- Ignition state
- Door ajar, liftgate or liftgate glass message from the SJB
Turn Signal Chime
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 IC provides a tick-tock tone along with the visual turn signal indicators.
The turn signal on warning chime inputs are the:
- RH/LH TURN or HAZARD signal messages from the SJB
Headlamps On Warning Chime
The headlamps on warning chime warns that the headlamps are on while the driver door is ajar. The headlamps on warning chime sounds when all the following conditions are met:
- The ignition switch is in the OFF/LOCK position
- The driver door is ajar
- The headlamp switch is in the PARK or HEADLAMPS position
- The key is out of the ignition lock cylinder
The headlamp on warning chime stops sounding when any one of these conditions are met:
- The ignition switch is placed in the RUN position
- The driver door is closed
- The headlamp switch is turned off
The headlamp on warning chime inputs are the:
- Ignition switch voltage
- Headlamp switch status message from the SJB
- LH front door ajar switch message from the SJB
- Key-in-ignition switch status message from the SJB
Key-In-Ignition Warning Chime
The key-in-ignition warning chime warns that the key is in the ignition when the LH front door is ajar. The key-in-ignition warning chime sounds when all the following conditions are met:
- The ignition switch is in the OFF/LOCK or ACC position
- The LH front door is ajar
- The key is in the ignition lock cylinder
The key-in-ignition warning chime stops sounding when the:
- LH front door is closed.
- Key is removed from the ignition lock cylinder.
- Ignition switch is turned to the RUN position.
The key-in-ignition warning chime inputs are the:
- Ignition state
- Key-in-ignition warning switch message from the SJB
- LH front door ajar switch
Message Center Warning Chime (If Equipped)
The message center warning chime sounds when the IC receives a new message to be displayed in the message center. The chime tone sounds once per ignition cycle for each message that is received. If there are multiple messages present upon key on, the IC provides a single, 1.0 second tone, for each message that displays. The message may remain visible, but the chime only sounds once.
The message center warning chime inputs are the message center warning messages received from external sensors and other modules.
Parking Brake On Warning Chime
The parking brake warning chime is controlled by the SJB and warns that the parking brake is applied with the vehicle in motion.
The parking brake warning chime input is the parking brake chime request from the SJB.
Perimeter Alarm Warning Chime
The perimeter alarm warning chime is used to alert the driver that the perimeter alarm is armed when the driver door is unlocked with a key. The warning chime is only functional when a key is used to unlock the driver door. If the key fob or keypad (if equipped) is used to unlock the door, the perimeter alarm is disarmed and the warning chime does not sound. The warning chime sounds for 12 seconds when the driver door is opened and turns off when the perimeter alarm is disarmed (either by using the key fob, keypad or turning the key to the ON position). After the 12-second warning chime duration, the warning chime stops sounding and the perimeter alarm activates, sounding the horn and flashing the turn signal lights.
NOTE: The perimeter alarm takes approximately 25 seconds to fully arm once the driver has locked the doors using the key fob or keypad.
Safety Belt Warning Chime
The safety belt warning chime warns that the driver safety belt is not fastened. The safety belt warning chime sounds when the driver safety belt is not fastened and the ignition switch is turned to the RUN or START position.
The safety belt warning chime stops sounding when the:
- Driver safety belt is fastened
- Ignition switch is turned to the OFF/LOCK or ACC position
- Chime has sounded 6 times
The safety belt warning chime inputs are the:
- Ignition state
- Driver safety belt switch message from the RCM
Turn Signal Left On Warning Chime
The turn signal left on warning chime warns that the turn signals have been left on. The turn signals must have been on continuously for more than 3.2 km (2.0 miles).
The turn signal left on warning chime inputs are the:
- Odometer rolling count message from the PCM
- RH or LH turn signal message from the SJB