Principles of Operation: Notes

WARNING: This page is about a different car, the 2005 Mercury Mountaineer and 2005 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

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 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 circuits transmits and receives data between the instrument cluster, the powertrain control module (PCM), the electronic automatic temperature control (EATC), the tire pressure monitoring system (TPMS) module, 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 driver seat module. For additional information regarding the CAN and UBP circuits, 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 circuits 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 prove-outs for 60-seconds or until the safety belt is fastened. The SERVICE ENGINE SOON, the charging system warning indicator, and the CHECK GAUGE warning indicator 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:

4x4 LOW indicator
4x4 HIGH indicator
ABS warning indicator
air bag warning indicator (6-seconds)
BRAKE warning indicator
electronic throttle control indicator
tire pressure monitoring system indicator
traction control indicator
HI TEMP LOW OIL warning indicator
CHECK FUEL CAP warning indicator