Antilock Brakes / Traction Control Systems: Description and Operation
Anti-Lock Control
ABS with Engine Only Traction Control (EOTC)
The anti-lock control system consists of the following components:
- ABS module - attached to the Hydraulic Control Unit (HCU), but can be serviced separately.
- Front wheel speed sensors - one sensor is located in each wheel bearing and wheel hub assembly and is serviced with the wheel bearing and wheel hub. For front wheel bearing and wheel hub removal and installation information, refer to Front Suspension Front Suspension.
- Front wheel speed sensor tone rings - one tone ring is located in each wheel bearing and wheel hub assembly and is serviced with the wheel bearing and wheel hub.
- HCU - located in the front, LH area of the engine compartment, underneath the Air Cleaner (ACL) assembly.
- Rear wheel speed sensors - one sensor is located in each rear brake caliper anchor plate. The sensors are serviced separately from the anchor plate.
- Rear wheel speed sensor tone rings - one tone ring is located on the end of each axle shaft and is serviced with the axle shaft. For axle shaft removal and installation information, refer to Rear Drive Axle/Differential - Ford 8.8-Inch Ring Gear Service and Repair.
- Stability/traction control switch - located on the LH instrument panel finish panel and is serviced separately from the finish panel.
Anti-Lock Control
The anti-lock control system aids in the prevention of wheel lock-up during braking events which will allow the driver to maintain steering control and stop in the shortest distance possible under most conditions. This is accomplished by the ABS module and HCU modulating brake fluid pressure to the affected brake caliper(s).
When the anti-lock control system activates, any of the following can occur and are considered to be normal operation:
- A rumble or grinding sound may be heard
- If the driver's foot is on the brake pedal, a vibration may be felt in the brake pedal
Engine Only Traction Control (EOTC) System
The Engine Only Traction Control (EOTC) system aids in the prevention of excessive wheel spin during acceleration which will allow the vehicle to maintain traction during acceleration. This is accomplished by the PCM modulating engine torque by reducing fuel injector pulses and ignition timing. The only function of the ABS in an EOTC system is to provide wheel speed information to the PCM along the High Speed Controller Area Network (HS-CAN) bus.
When the EOTC system activates, any of the following can occur and are considered to be normal operation:
- A small deceleration or a reduction in the acceleration of the vehicle
- The stability/traction control indicator ("sliding car" icon) flashes
Stability/Traction Control Switch
The stability/traction control switch can be used by the driver to disable and enable the EOTC system. When the switch is pressed, the system is disabled. When the system is disabled, the stability/traction control indicator ("sliding-car icon") in the Instrument Cluster (IC) (or message center if equipped) will illuminate and the LED indicator on the switch will illuminate. The standard anti-lock control system cannot be disabled through the use of the stability/traction control switch.