Principles of Operation

When installing a new instrument cluster, it is necessary to upload the module configuration to the diagnostic tool. Following installation of the new instrument cluster, download the module configuration from the diagnostic tool into the new instrument cluster. For additional information, refer to MODULE CONFIGURATION . The following items are configurable:

• overspeed warning
• belt minder
• 4x4 feature
• speedometer scaling
• electronic automatic temperature control (EATC)
• default language
• trailer brake controller
• transit mode
• tank configuration

The instrument cluster is a configurable, hybrid electronic cluster (HEC) that contains a microprocessor, gauges, indicator lamps, and internal circuitry. The instrument cluster is non-repairable, with the exception of the instrument cluster lens, the warning bulbs, and the transmission range selector. The instrument cluster uses hardwired circuitry, the controller area network (CAN), and universal asynchronous receiver transmitter (UART)-based protocol (UBP) communication networks. Communication using the CAN uses data transmitted and received between the instrument cluster, the trailer brake control (TBC) electronic control unit, the powertrain control module (PCM), and the anti-lock brake system (ABS) module. Communication using the UBP network uses data transmitted and received by the instrument cluster, the vehicle security module, and the electronic automatic temperature control (EATC). For additional information regarding the communication network, refer to MODULE COMMUNICATIONS NETWORK .

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 or UBP network to another module.
• which module controls the output of the feature.

The instrument cluster carries out a display prove-out to verify that the warning/indicator lamps and monitored systems are operating correctly. The safety belt warning indicator proves-out for 65-seconds or until the safety belt is fastened. The malfunction indicator lamp (MIL), and the wait to start indicator (diesel engines) illuminate continuously until the engine is started and operating normally. When the ignition switch is turned to the ON position with the engine off, the following indicators illuminate for 3 seconds:

• LOW RANGE indicator
• 4x4 indicator
• BRAKE warning indicator
• ABS warning indicator
• charging system warning indicator
• door ajar indicator
• air bag warning indicator (6 seconds)
• electronic throttle control