Charging Indicator: Operation

WARNING: This page is about a different car, the 2004 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.

The charging indicator gives an indication to the vehicle operator when the electrical system voltage readings reflect a condition requiring immediate attention. This 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. The charging indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and that logic will; only allow this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the LED will always be off when the ignition, switch is in any position except On or Start. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The instrument cluster will turn on the charging indicator for the following reasons:

Bulb Test - Each time the ignition switch is turned to the On position the charging indicator is illuminated for about two seconds as a bulb test.
System Voltage Low (Charge Fail) Message - Each time the cluster receives a message from the PCM indicating the electrical system voltage is less than about 11.5 volts (charge fail condition), the charging indicator will be illuminated. The indicator remains illuminated until the cluster receives a message from the PCM indicating the electrical system voltage is greater than about 12.0 volts (but less than 16.0 volts), or until the ignition switch is turned to the Off position, whichever occurs first.
System Voltage High Message - Each time the cluster receives a message from the PCM indicating the electrical system voltage is greater than about 16.0 volts, the charging indicator will be illuminated. The indicator remains illuminated until the cluster receives a message from the PCM indicating the electrical system voltage is less than about 15.5 volts (but greater than 11.5 volts), or until the ignition switch is turned to the Off position, whichever occurs first.
Actuator Test - Each time the cluster is put through the actuator test, the charging indicator will be turned on, then off again during the bulb check portion of the test to confirm the functionality of the LED and the cluster control circuitry.

The PCM continually monitors the system voltage to control the generator Output. The PCM then sends the proper system voltage messages to the instrument cluster. For further diagnosis of the charging indicator or the instrument cluster circuitry that controls the LED, (Refer to DIAGNOSIS AND TESTING - INSTRUMENT CLUSTER ). If the instrument cluster turns on the charging indicator due to a charge fail or voltage high condition, it may indicate that the charging system requires service. For proper diagnosis of the charging system, the PCI data bus, or the electronic message inputs to the instrument cluster that control the charging indicator, a DRBIII(R) scan tool is required. Refer to ELECTRONIC CONTROL MODULES .