An Electronic Throttle Control (ETC) indicator is standard equipment on all gasoline engine instrument clusters. However, on vehicles not equipped with the optional 5.7 liter gasoline engine, this indicator is electronically disabled. The Electronic Throttle Control (ETC) indicator gives an indication to the vehicle operator when the ETC system is faulty or inoperative. The ETC indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus.For proper diagnosis of the ETC system, the PCM, the PCI data bus, or the electronic message inputs to the instrument cluster that control the ETC indicator, a diagnostic scan tool is required. For this reason, it is recommended that you take your vehicle to your Local Dealership for inspections and Diagnosis.