Charging Indicator - Operation

OPERATION

The charging indicator gives an indication to the vehicle operator when the electrical system voltage is too low. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster over the Controller Area Network (CAN) data bus from the Body Control Module (BCM) (also known as the Signal Acquisition and Actuation Module/SAM).

The charging indicator Light Emitting Diode (LED) or icon and textual message display are completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate or icon and textual message to be displayed when the instrument cluster detects that the ignition switch is in the ON position. Therefore, the LED or the icon and textual message will always be OFF when the ignition switch is in any position except ON. The LED only illuminates or the icon and textual message are only displayed when it is activated by the instrument cluster logic. The instrument cluster will turn ON the charging indicator for the following reasons:

- Bulb Test - On vehicles not equipped with the optional steering wheel buttons, each time the ignition switch is turned to the ON position with the engine not running the charging indicator is illuminated by the cluster briefly as a bulb test.
- Charging Indicator Lamp-On Message - On vehicles not equipped with the optional steering wheel buttons, each time the cluster receives an electronic charging indicator lamp-ON message from the BCM while the engine is running indicating that the battery is not being charged, the charging indicator will be illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message from the BCM, or until the ignition switch is turned to the OFF position, whichever occurs first. On vehicles equipped with the optional steering wheel buttons, each time the cluster receives an electronic charging indicator lamp-ON message from the BCM, an icon and a Battery/Alternator - Visit workshop textual message will appear within the cluster multi-function display. The icon and textual message remain displayed until the cluster receives a lamp-OFF message from the BCM, or until the ignition switch is turned to the OFF position, whichever occurs first.

The BCM continually monitors the generator output and engine speed to decide whether the charging system is in good operating condition. The BCM then sends the proper lamp-ON or lamp-OFF messages to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN or KOMBI). If the BCM sends a lamp-ON message after the bulb test while the engine is running, it indicates that the charging system may require service.

For proper diagnosis of the charging system, the BCM, the EMIC, the CAN data bus or the electronic communication related to charging indicator operation, a diagnostic scan tool is required. Refer to the appropriate diagnostic information.