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 Medium Speed Controller Area Network (MS-CAN) and the High Speed Controller Area Network (HS-CAN) bus lines and through hardwired circuitry from individual components. The IC uses each input to output an action to the gauges or indicators. 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.
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 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. 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 the Programmable Module Installation (PMI) procedure. Refer to Programmable Module Installation (PMI) in Information Bus. Programming and Relearning
The configurable IC customer preference items are as follows:
- Default language
- Oil life threshold
- Belt-Minder(R)
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, informational indicators, and warning indicators. The message center, located in the center of the 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 warning messages 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.
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. Generally, 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.
Instrument Cluster (IC) Chime Characteristics:
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, 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
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
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, 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 5 minutes.
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 or front 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 5 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, repeating for up to 5 minutes.
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 IC sounds 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
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
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 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 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
Memory Set Chime
The memory feedback chime is to inform the driver that their preferences have been programmed through the memory set procedure.
Memory set chime inputs are:
- Ignition switch RUN/START status
- Memory feedback chime request communicated by the Driver Seat Module (DSM) over the MS-CAN