Principles of Operation

PRINCIPLES OF OPERATION

The instrument cluster (IC) gauges are not installed separately from the instrument cluster (IC). The instrument cluster (IC) illumination lamps, warning indicator lamps, transmission range selector, and the instrument cluster (IC) lens is the only part that may be installed separately.

The instrument cluster (IC) is a hybrid electronic cluster (HEC) that uses a microprocessor to control the gauge and indicator functions. The instrument cluster (IC) receives its inputs from modules and components through hardwired circuitry and the high speed controller area network (HS-CAN) bus. The instrument cluster (IC) uses each input to control an output through the gauges and indicators.

Instrument Cluster (IC) Network Messages

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 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 some of the gauges and 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 engine rpm data is missing for less than 5 seconds and the engine was running at 1,000 rpm, the tachometer remains at 1,000 rpm until the next valid 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. In the example above, the tachometer defaults to 0 rpm. 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.
- whether the module which received the input controls the output of the feature, or whether it outputs a message over the CAN circuits to another module.
- which module controls the output of the feature.

Instrument Cluster (IC) Prove-Out
The instrument cluster (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 instrument cluster (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: