Module, Anti-Lock Brake System (Abs): Operation: Notes
The Electronic Stability Control (ESC) may also be referred to as Electronic Stability Program (ESP) depending on the vehicle model year and configuration. Certain components may also reference ESP, ESC, or use the traction control symbol.
The primary functions of the Antilock Brake System (ABS) module are to:
- Monitor the antilock brake system for proper operation.
- Detect wheel locking or wheel slipping tendencies by monitoring the speed of all four wheels of the vehicle.
- Control fluid modulation to the wheel brakes while the system is in an ABS mode.
- Store diagnostic information.
- Provide communication to the scan tool while in diagnostic mode.
- Illuminate the amber ABS warning indicator lamp.
- Illuminate the ESC function lamp in the message center on the instrument panel when a traction control event occurs.
- Illuminate the ESC function lamp when the amber ABS warning indicator lamp illuminates.
The ABS module constantly monitors the antilock brake system for proper operation. If the ABS module detects a fault, it will turn on the amber ABS warning indicator lamp and disable the antilock braking system. The normal base braking system will remain operational.
If the vehicle is equipped with traction control, the ESC function lamp will illuminate anytime the amber ABS warning indicator lamp illuminates.
The ABS module continuously monitors the speed of each wheel through the signals generated by the wheel speed sensors to determine if any wheel is beginning to lock. When a wheel locking tendency is detected, the ABS module commands the coils to actuate. The coils then open and close the valves in the HCU that modulate brake fluid pressure in some or all of the hydraulic circuits. The ABS module continues to control pressure in individual hydraulic circuits until a locking tendency is no longer present.
The ABS module contains a self-diagnostic program that monitors the antilock brake system for system faults. When a fault is detected, the amber ABS warning indicator lamp is turned on and the fault diagnostic trouble code (DTC) is then stored in a diagnostic program memory. A latched fault will disable certain system functionality for the current ignition cycle. An unlatched fault will disable certain system functionality until the fault condition disappears. These DTC's will remain in the ABS module memory even after the ignition has been turned off. The DTC's can be read and cleared from the ABS module memory by a technician using a scan tool. If not cleared with a scan tool, the fault occurrence and DTC will be automatically cleared from the ABS module memory after the identical fault has not been seen during the next 3, 500 miles. Drive-off may be required for the amber ABS warning indicator lamp to go out on the next ignition cycle.