Principles of Operation

PRINCIPLES OF OPERATION

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

The instrument cluster (IC) uses inputs that are both hardwired to individual components and messages that are sent from the other modules over the high speed or medium speed controller area networks (HS-CAN or MS-CAN) to control the warning chime functions.

It is very important to understand:
- where the input (command) originates.
- all the information (messages) necessary in order for a feature to operate.
- which module(s) receive(s) the input or command message.
- if the module that received the input (message) controls the output of the feature, or if it outputs a message over the CAN to another module.
- which module controls the output of the feature.

Instrument Cluster (IC) Network Messages

NOTE: Whenever a network message is suspected as missing, confirmed by a missing message DTC, 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 Information Bus (Module Communications Network) 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) uses input messages from other modules to control the gauges, informational indicators, warning indicators and reconfigurable telltale 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 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 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.

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.

Safety Belt Warning Chime
The safety belt warning chime is activated when the ignition switch is in the RUN position and the RCM detects an unbuckled driver safety belt. The instrument cluster (IC) generates the chime for a duration of 6 seconds or until the safety belt is buckled.

Belt-Minder(R)

NOTE: The Belt-Minder(R) is a configurable item. To configure without using a scan tool, refer to Belt-Minder(R) Deactivating/Activating.

The Belt-Minder(R) feature supplements the current safety belt warning function. The Belt-Minder(R) feature is enabled after the current safety belt warning is complete. The Belt-Minder(R) reminds the driver that his/her 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). While activated, the Belt-Minder(R) alternates the chime and indicator from ON for 6 seconds, to OFF for 30 seconds.

The Belt-Minder(R) reminder stops when:
- the driver or passenger safety belt is buckled.
- the ignition switch is turned to the OFF or ACC position.
- five minutes have elapsed since Belt-Minder(R) has started.

Key-In-Ignition Warning Chime
When the key-in-ignition switch closes, it sends a voltage signal to the instrument cluster (IC), which then sounds a warning chime, provided the ignition key is in the ignition lock cylinder, the ignition switch is in the OFF position, and the driver door is open. The instrument cluster (IC) sounds a steady tone, which continues until the key is removed, the ignition switch is rotated to the RUN position, or the driver door is closed.

Air Bag Warning Chime
The air bag warning chime warns the driver that a fault has occurred in the supplemental restraints system (SRS) and that the air bag warning indicator lamp is not working by sounding a chime when the ignition switch is in the RUN position for more than 20 seconds. When these conditions exist, the restraints control module (RCM) sends a chime request through the communication network to the instrument cluster (IC). The instrument cluster (IC) then activates the warning chime. The warning consists of 5 sets of five 1-second tone bursts. Each set is separated by 5 seconds of silence. The warning is repeated every 30 minutes.

Door/Trunk Ajar Warning Chime
The door/trunk ajar warning chime warns that a door, or the trunk, is not fully closed. The chime sounds when any door or the trunk becomes ajar while the ignition switch is in the RUN position.

Headlamps On Warning Chime
The headlamps on warning chime is activated when the instrument cluster (IC) receives the parking lamps ON message from the SJB, the key is out of the ignition, and the driver door is ajar. The warning consists of repeated one-half second bursts and continues to sound until the exterior lamps are turned off, the driver door is closed, or 10 minutes have elapsed, at which time the battery saver turns the exterior lamps off.

Message Center Warning Chime
The message center warning chime accompanies any initial warning message display, as well as any repeated initial warning message. As the message center is an integral part of the instrument cluster (IC), the interaction between the message center and the chime function is also integral to the instrument cluster (IC).

The message center switch tone sounds when any switch on the message center is pressed. The message center switches are supplied with a voltage reference signal from the instrument cluster (IC). When a switch is pressed, it routes the signal through a specific resistor in the switch assembly and then to ground.

Performance Shift Warning Chime
The performance shift warning chime provides an audible alert to inform the driver to shift the transmission gear. The chime is configured through the message center independently of the visual performance shift indicator. The chime feature on/off status and the desired rpm for the chime to sound are configurable items. The instrument cluster (IC) uses engine data rpm sent to the instrument cluster (IC) over the high speed controller area network (HS-CAN) communication lines and compares the value against the customer preset engine rpm to determine when to sound the chime. When the actual engine rpm matches the preset engine rpm, the instrument cluster (IC) sounds the chime.