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).
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 Information Bus 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 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), the Medium Speed Controller Area Network (MS-CAN) and through hardwired circuitry from individual components. The IC uses each input to output an action to the gauges or indicators.
The IC uses input messages from other modules to control the gauges, informational indicators, warning indicators and message center 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 brake status message is missing for less than 5 seconds and the brake warning 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 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 IC returns at any time, the normal function of the gauge or indicator resumes.
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 HS-CAN, converts the data into an MS-CAN message and sends (gateways) the message to other network modules such as the HVAC module, the Audio Control Module (ACM), and the SJB. This enables network communication between modules that do not communicate using the same network (HS-CAN or the MS-CAN).
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 Information Bus.
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 Information Bus to carry out PMI. It is also necessary to carry out a parameter reset procedure whenever a new IC or PCM is installed. Refer to Antitheft and Alarm Systems. Programmable Module Installation (PMI) Passive Anti-Theft System (PATS)
The following are the configurable customer preference items:
- Auto lock
- Auto-unlock
- Belt-Minder(R)
- Language
- Oil life warning threshold
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 to 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, informational indicators, and warning indicators. The message center, located in the center of the 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 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 IC gauges and indicators.
Trailer Sway Message
The message center provides the trailer sway message to inform the driver that the current traction control event is due to trailer sway. If the ABS module determines that the trailer is causing the vehicle to sway, the traction control/stability assist indicator is turned on along with the TRAILER SWAY REDUCE SPEED message in the message center.
Warning Chimes
The IC uses different chimes to alert the driver of various vehicle conditions as follows:
- Safety belt warning (repetitive chime)
- Belt-Minder(R) warning (repetitive chime after a delay and after the safety belt chime is completed)
- Key-in-ignition warning (repetitive chime)
- Headlamps on warning (repetitive chime)
- Turn signal on warning (single tone chime after 3.2 km [2 miles])
- Turn signal tone (tick-tock chime)
- Parking brake warning (repetitive chime)
- Air bag secondary warning chime (repetitive chime)
- Message center general tone (single tone)
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 safety belt is not fastened and the ignition key is turned from the OFF/LOCK or ACC to the RUN or START position.
The safety belt warning chime stops sounding when the safety belt is fastened, when the ignition key is turned from the RUN 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 the:
- Ignition switch RUN/START status
- Driver safety belt switch data communicated by the Restraints Control Module (RCM) to the IC through the HS-CAN
Belt-Minder(R)
The Belt-Minder(R) is configurable. To configure using a scan tool, refer to Information Bus. To configure without using a scan tool, refer to Belt-Minder(R) Deactivating/Activating Service and Repair.
The Belt-Minder(R) feature supplements the current safety belt warning function. The Belt-Minder(R) is enabled after the current safety belt warning is complete. The Belt-Minder(R) 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 IC once the vehicle speed exceeds 4.8 km/h (3 mph). While activated, the Belt-Minder(R) alternates the chime and indicator from on for 6 seconds to off for 60 seconds.
NOTE: The Belt-Minder(R) is disabled for one ignition switch on cycle if the safety belt is buckled then unbuckled during that specific cycle.
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 key is turned to the RUN position.
The key-in-ignition warning chime inputs are the:
- Ignition switch RUN/START status
- Door ajar data communicated by the SJB to the IC through the MS-CAN
- Key-in-ignition switch signal from the ignition switch
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 HEADLAMP or PARKING LAMP on position, and the ignition switch is in the OFF/LOCK position.
The headlamps on warning chime stops sounding when any one of the above conditions are removed.
The headlamps on warning chime inputs are the:
- Ignition switch RUN/START status
- Driver door ajar data communicated by the SJB to the IC through the MS-CAN
- Headlamp switch data communicated by the SJB to the 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 miles).
The turn signal on warning chime stops sounding if the turn signal is turned off, or if the ignition key is turned to the OFF or ACC position.
The turn signal on warning chime inputs are the:
- Turn signal data communicated by the SJB to the IC through the MS-CAN communication
- Odometer count data communicated by the PCM to the IC through the MS-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 key is in the RUN position, the parking brake is engaged, and the vehicle speed is greater than 4.8 km/h (3 mph).
The parking brake warning chime stops sounding if the parking brake is released, the ignition key is not in the RUN position, or if the vehicle speed is less than 4.8 km/h (3 mph).
The parking brake warning chime inputs are the:
- Ignition switch RUN/START status
- Parking brake switch data communicated by the SJB to the IC through the MS-CAN
- Vehicle speed data communicated by the PCM to the IC through the MS-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 IC monitors the air bag warning indicator status internally. When a fault is present in the air bag warning indicator and the 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 the:
- Ignition switch RUN/START status
- Air bag warning indicator request data communicated by the RCM to the IC through the HS-CAN
Turn/Hazard On Tone
The turn/hazard on tone provides an audible tick-tock in addition to the turn/hazard indicator lamps. The turn/hazard on tone sounds if the turn or hazard signals are on.
The turn/hazard on tone inputs are the:
- Left turn indicator signal from the SJB to the IC
- Right turn indicator signal from the SJB to the IC
Message Center Warning Chime
The message center warning chime sounds when a new warning message is displayed on the message center. If multiple warning messages are present, a chime tone sounds for each of the warnings that are displayed. The message center warning chime inputs are the warning messages displayed on the message center. The message center warning chime sounds to alert the driver when a concern is detected in one of the following systems:
- Tire Pressure Monitoring System (TPMS)
- Door ajar
- Low fuel level