Regenerative Brake Indicator - Operation

OPERATION

The Regenerative Brake System (RBS) indicator gives an indication to the vehicle operator when the RBS system, or a circuit or component of the system is ineffective. 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 Regenerative Brake Controller (RBC) (also known as the Controller Antilock Brake/CAB) over the Controller Area Network (CAN) data bus.

The RBS indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit. This logic only allows the indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the LED is always 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 turns on the RBS indicator for the following reasons:

- Bulb Test - Each time the ignition switch is turns to the on position the RBS indicator is illuminated for about four seconds as a bulb test. The entire bulb test is a function of the RBC.
- RBS Indicator Lamp-On Message - Each time the cluster receives an electronic RBS indicator lamp-on message from the RBC, the RBS indicator illuminates. The indicator remains illuminated until the cluster receives a lamp-off message from the RBC, or until the ignition switch turns to the OFF position, whichever occurs first.
- Communication Error - If the cluster receives no lamp-on or lamp-off messages from the RBC for five consecutive message cycles, the RBS indicator is illuminated. The indicator remains illuminated until the cluster receives a valid message from the RBC, or until the ignition switch is turned to the OFF position, whichever occurs first.
- Self Test - Each time the instrument cluster is put through the self test, the RBS indicator turns on, then off again during the bulb check portion of the test to confirm the functionality of the LED and the cluster control circuitry.
- RBS Diagnostic Test - The RBS indicator is blinked on and off by lamp-on and lamp-off messages from the RBC during the performance of the RBS diagnostic tests.

The RBC continually monitors the RBS circuits and sensors to decide whether the system is in good operating condition. The RBC then sends the proper lamp-on or lamp-off message to the instrument cluster, also known as the Cab Compartment Node (CCN). If the RBC sends a lamp-on message after the bulb test, it indicates that the RBC has detected a system malfunction or that the RBS system has become ineffective. The RBC stores a Diagnostic Trouble Code (DTC) for any malfunction it detects. Each time the RBS indicator fails to light due to an open or short in the cluster RBS indicator circuit, the cluster sends a message notifying the RBC of the condition, then the instrument cluster and the RBC will each store a DTC.

Use a diagnostic scan tool for proper diagnosis of the regenerative brake system, the RBC, the CCN, the CAN data bus or the electronic communication related to RBS indicator operation. Refer to the appropriate diagnostic information.