Charging Indicator

WARNING: This page is about a different car, the 2017 RAM 2500 HD. 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 is too low or too high. This indicator is controlled by the Instrument Panel Cluster (IPC) based upon cluster programming and electronic messages received over the Controller Area Network (CAN) data bus. These electronic messages are received from the Powertrain Control Module (PCM) or Engine Control Module (ECM), depending on engine application.

The charging indicator Light Emitting Diode (LED) is completely controlled by the IPC logic circuit, and that logic will only allow this indicator to operate when the IPC 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 a transistor on the IPC circuit board. Each time the ignition switch is turned to the ON position the charging indicator is illuminated by the IPC for about two seconds as a bulb test. The charging indicator will be turned ON for the following reasons:

Voltage Low Message - Each time the IPC receives an electronic system voltage message from the PCM or ECM indicating the voltage is low (less than about 11.5 volts is a charge fail condition), the charging indicator will be illuminated. The indicator remains illuminated until the cluster receives a message from the PCM indicating the voltage is normal (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.
Voltage High Message - Each time the IPC receives an electronic system voltage message from the PCM or ECM indicating the voltage is high (greater than about 16.0 volts), the charging indicator will be illuminated. The indicator remains illuminated until the IPC receives a message from the PCM or ECM indicating the voltage is normal (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.

The PCM or ECM continually monitors the electrical system voltage to control the generator output. The PCM or ECM then sends the proper messages to the IPC. If the charging indicator is turned ON due to a charge fail or voltage high condition, it may indicate that the charging system requires service. For further diagnosis of the charging indicator or the IPC circuitry that controls the indicator. Refer to DIAGNOSIS AND TESTING .