Principles of Operation

PRINCIPLES OF OPERATION

The instrument cluster 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 Messages

NOTE: Whenever a 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 and throughout the vehicle. Once a DTC is set in the instrument cluster 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 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 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 instrument cluster 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.

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 instrument cluster prioritizes the chimes according to a preset hierarchy programmed into the instrument cluster software. When more than one chime request is received by the instrument cluster, 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
- Tic-toc

Instrument Cluster Chime Characteristics/Priority:

The table provides a summary of the chime characteristics including the chime priority.

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 switch RUN/START position
- Ignition switch RUN/ACC position
- Driver safety belt switch message from the restraints control module (RCM)

Air Bag Warning Chime
The air bag warning chime warns that a fault is present within the air bag warning indicator circuit. The RCM provides the air bag warning indicator message to the instrument cluster. The instrument cluster 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.

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 LH front door is ajar
- The key is in the ignition lock cylinder
- The ignition switch is in the OFF/LOCK or ACC position

The key-in-ignition warning chime will stop 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 switch RUN/START position
- Ignition switch RUN/ACC position
- Key-in-ignition warning switch message from the smart junction box (SJB)
- LH front door ajar switch

Turn Signal Left On Warning Chime
The turn signal left on warning chime warns that the turn signals have been left on. The turns 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 powertrain control module (PCM)
- RH or LH turn signal message from the SJB

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 switch RUN position
- 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 instrument cluster provides an tic-toc 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 headlamp on warning chime warns that the headlamps are on while the driver door is ajar. The headlamp on warning chime sounds when all the following conditions are met:
- The driver door is ajar
- The headlamp switch is in the PARK or HEADLAMPS position
- The ignition switch is in the OFF/LOCK position
- The key is out of the ignition lock cylinder

The headlamp on warning chime stops sounding when any one of the conditions are met:
- The driver door is closed
- The headlamp switch is turned off
- The ignition switch is placed in the RUN position

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

Message Center Warning Chime (If Equipped)
The message center warning chime sounds when the instrument cluster 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 instrument cluster 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.

Belt Minder Warning Chime
The safety belt minder feature is configurable. To configure without using a scan tool, refer to Safety Belt Minder Deactivating/Activating. Service and Repair

The safety belt minder feature is controlled by a message sent to the instrument cluster from the RCM and supplements the safety belt warning chime and the safety belt warning indicator functions. The safety belt minder 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. The safety belt minder 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 safety belt minder 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 remains active after 3 repetitions, the sound level and the speed of the chimes increase.

The safety belt minder warning chime inputs are the:
- Ignition switch RUN/START position
- Ignition switch RUN/ACC position
- Driver safety belt switch message from the RCM

The safety belt minder reminder stops when:
- the driver safety belt is buckled.
- the ignition switch is turned to the OFF or ACC position.