Abs Indicator

The ABS (Antilock Brake System) indicator indicates when an ABS circuit, or component of the system, is inoperative. This indicator is controlled by a transistor on the IPC circuit board based upon IPC programming and electronic messages received by the IPC from the ABS module over the CAN data bus.

The ABS indicator Light Emitting Diode (LED) is completely controlled by the IPC logic circuit, and the logic will only allow the 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 the IPC transistor. Each time the ignition switch is turned to the ON position the ABS indicator illuminates for approximately three seconds. The IPC will turn ON the ABS indicator for the following reasons:

• ABS Indicator Lamp-On Message  - Each time the IPC receives an electronic ABS indicator lamp-ON  message from the ABS module, the ABS indicator will be illuminated. The indicator remains illuminated until the IPC receives a lamp-OFF message from the ABS module, or until the ignition switch is turned to the OFF position, whichever occurs first.
• Communication Error  - If the IPC does not receive a lamp-ON or lamp-OFF message from the ABS module for five consecutive message cycles, the ABS indicator is illuminated. The indicator remains illuminated until the IPC receives a valid message from the ABS module, or until the ignition switch is turned to the OFF position, whichever occurs first.
• ABS Diagnostic Test  - The ABS indicator is illuminated ON and OFF by lamp-ON and lamp-OFF messages from the ABS module during the performance of the ABS diagnostic tests.

The ABS module continually monitors the ABS circuits and sensors to determine if the system is operating properly. The ABS module then sends the proper lamp-ON or lamp-OFF message to the IPC. If the ABS module sends a lamp-ON message, after the bulb test, it indicates that the ABS module detects a system malfunction or an inoperative system. The ABS module will store a Diagnostic Trouble Code (DTC) for any malfunction it detects. Each time the ABS indicator fails to light due to an open or short in the ABS indicator circuit, the IPC sends a message notifying the ABS module of the condition. The IPC and the ABS module will each store a DTC and the IPC will flash the brake indicator ON and OFF as a backup to notify the vehicle operator.