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) bus, Medium Speed Controller Area Network (MS-CAN) bus 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 HS-CAN, converts the data into a MS-CAN message and sends (gateways) the message to other network modules such as the HVAC, 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 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 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 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 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 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.
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 only be set by 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. Programming and Relearning Passive Anti-Theft System (PATS) Parameter Reset
The configurable IC items are as follows:
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 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, 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 FRONT DOOR AJAR along with the door ajar message center warning indicator. This allows the message center to be a more informative supplement to the IC gauges and indicators.
Warning Chimes
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.
IC Chime Characteristics
Safety Belt Warning Chime
The safety belt warning chime warns that the driver side safety belt is not fastened. The safety belt warning chime sounds when the driver 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 safety belt warning request communicated by the Restraints Control Module (RCM) to the IC through the HS-CAN.
- Driver safety belt warning chime request communicated by the RCM to the IC through the HS-CAN.
Belt-Minder(R)
The Belt-Minder(R) is configurable. 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 and is enabled after the current safety belt warning is complete. The Belt-Minder(R) reminds the driver that the driver safety belt is unbuckled by intermittently sounding a chime and illuminating the safety belt warning lamp in the IC once the vehicle speed has exceeded 4.8 km/h (3 mph), and remains active for 5 minutes from the time it is started. While activated, the Belt-Minder(R) chime and indicator flash and chime simultaneously from on for 6 seconds to off for 30 seconds.
NOTE: The Belt-Minder(R) 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(R) warning chime inputs are the:
- Ignition switch RUN/START status.
- Safety belt warning request communicated by the RCM to the IC through the HS-CAN.
- Belt-Minder(R) chime request communicated by the RCM to the 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 IC monitors the air bag warning indicator status internally and provides an air bag indication status report to the RCM. When a fault is present in the Supplemental Restraint System (SRS) with the RCM sending the IC an air bag warning indicator on request and a fault is detected in the air bag warning indicator, the RCM sends the IC a secondary request to sound the air bag warning chime.
The air bag secondary warning chime inputs are:
- Ignition switch RUN/START status.
- Air bag warning indicator request communicated by the RCM to the IC.
- Air bag warning indicator chime request communicated by the RCM to the IC.
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, if the ignition switch is turned to the ON position, or the battery saver has expired.
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 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 IC through the MS-CAN communication.
- Odometer count data communicated by the PCM to the IC through the HS-CAN.
Turn/Hazard On Tone
Since the turn/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/hazard on tone inputs are:
- Left turn indicator signal from the SJB to the IC through the MS-CAN.
- Right turn indicator signal from the SJB to the IC through the MS-CAN.
- Hazard signal from the SJB to the IC through the MS-CAN.
Headlamps On Warning Chime
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.
The headlamps on warning chime stops sounding when any one of the above conditions are removed or the battery saver has expired.
The headlamps on warning chime inputs are:
- 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 IC through the MS-CAN.
Message Center Warning Chime
The message center warning chime feature is to draw the driver's attention to the message center display to view each new warning message. The IC provides a single one-second tone whenever a new warning message is displayed in the message center. If multiple warning messages are present, the IC sounds a chime for each of the warning messages that are present.
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.
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 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 and resets if the parking brake is released, the ignition switch is not in the ON position, if the vehicle speed is less than 4.8 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 IC through the MS-CAN.
- Vehicle speed data communicated by the PCM to the IC through the HS-CAN then to the SJB through the MS-CAN.
- Parking brake warning chime request communicated by the SJB to the IC.
Low Fuel Warning Chime
The low fuel chime sounds when the Distance To Empty (DTE) calculation reaches 80 km (50 miles) or less. The DTE is calculated internally by the IC from data received from the PCM and fuel level input. When the IC receives the data, the fuel gauge indicates low fuel and the IC sounds the low fuel warning chime.
The low fuel warning chime inputs are:
- Ignition status.
- DTE calculated mileage.