ESP Indicator - Operation

OPERATION

The Electronic Stability Program (ESP) indicator gives an indication to the vehicle operator when the ESP 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 over the Controller Area Network (CAN) data bus from the Controller Antilock Brake (CAB) (also known as the Antilock Brake System/ABS or Electronic Stability Program/ESP controller).

The ESP 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 detects that the ignition switch is in the ON position. Therefore, the LED will always be OFF when the ignition switch is in any position except ON. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The instrument cluster will turn ON the ESP indicator for the following reasons:

- Bulb Test - Each time the ignition switch is turned to the ON position the ESP indicator is illuminated by the cluster briefly as a bulb test.
- ESP Indicator Lamp-On Message - Each time the cluster receives an electronic ESP indicator lamp-ON message from the CAB indicating that the ESP system has been deactivated, the ESP indicator will be illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message from the CAB, 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 ESP indicator lamp-ON message from the CAB, the ESP indicator will be illuminated and a Visit workshop or unavailable textual message will appear within the cluster multi-function display. The indicator and textual message remain displayed until the cluster receives a lamp-OFF message from the CAB, or until the ignition switch is turned to the OFF position, whichever occurs first.

The CAB continually monitors the ESP system circuits and sensors to decide whether the system is in good operating condition. The CAB 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 CAB sends a lamp-ON message after the bulb test, it indicates that the CAB has detected a system malfunction or that the ESP system has become ineffective. The CAB will store a Diagnostic Trouble Code (DTC) for any malfunction it detects.

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