“Vehicle Stability Control – ESP-VSC-ABS Brake Concepts for Pass Car & Light Trucks”

VSC intervention; Driver is loosing control of vehicle in a left turn! The driver typically then rotates the steering wheel with more left turn input (20-30-40 degrees additional rotation). The Steering Sensor and the YAW sensor now disagree, the vehicle is in a skid, even if the driver is stepping on the throttle. Stability Control (DSC) Intervention is now activated!

- Driver notification begins (flashing ESP light on dash) - Electric Throttle is closed reducing acceleration. Transmission downshift may occur. - Individual wheels are braked at 400 millisecond intervals (Left front and Right rear).

As correction becomes successful, the steering sensor tells the VSC module when “straight ahead” begins to be restored (driver straightens the wheel). System then de-activates when steering sensor and YAW sensor agree. Braking activity is reduced, throttle inputs are restored, directional control corrections are completed, flashing ESP dash light is turned off, and the vehicle is again traveling normally!

Friction choices for Stability Controlled equipped vehicles are VERY important.

If the friction “MU” characteristics are different than OE, the vehicle may not react properly to individual wheel braking. VSC intervention may not accomplish needed corrections, and an accident may occur! Wagner ThermoQuiet is now reformulated to meet and exceed OE friction effectiveness requirements (Fade Minimum MU Criteria - FMVSS135) for Stability Control equipped vehicles!

Stability Control Systems use Steering Wheel Sensors which may need to be “recalibrated” after suspension repairs. These sensors may not understand true “straight ahead” steering wheel position, therefore may cause the VSP module to perform unwanted aggressive intervention which can cause abrupt and aggressive corrections. Accelerometer Sensors, Electronic Throttle System, Magneto Resistive Wheel Speed Sensors (Digital Output Sensors), Suspension Height Sensors, etc., are additional components used with ESC. Steering Wheel Sensor Recalibration can be performed with updated hand-held scanners or NEW technology alignment equipment.

Electronic Brake Force Distribution (EBD) and the removal of proportioning valves . For many years, common ABS systems have used hydraulic “redundant” pressure reduction valves (Proportioning Valves) in the rear brake circuit in the event of an ABS system shutdown. Proportioning Valves manually reduce rear hydraulic brake fluid pressure during a panic stop due to less weight distribution in the rear and more weight distribution toward the front. Newer DSC systems now use EBD which performs rear wheel pressure reduction or increase electronically. Due to the OEMs eliminating the backup valves, if an ABS malfunction were to occur, no manual pressure reduction control exists, and rear wheel lock-up can happen. This situation can cause unwanted lane change during a panic stop. If the amber or red light is on, brake pressure is now only driver controlled, as ABS is inactive (fault code) and no valve exists.

Lower control arm “compliance bushings” assist with lane correction during Stability Control “Individual Wheel Braking.” Lower Control Arm Rear Bushing flex can allow up to “1 inch toe out” per front wheel, helping to steer the car back on the road.

TPMS – Tire Pressure Monitor Systems are utilized in combination with ESC/VSC/ABS

Electronic Parking Brake Calipers and Rear Disc Pad service techniques . Caliper piston retraction procedures for rear disc pad service on vehicles equipped with Electric Parking Brake Calipers. Leaving the engine running during service may help keep the piston “home” after retraction. Friction service cannot be performed until scan tool piston retraction takes place first.

Wagner Friction now offers Specific Ceramic NAO (QC-PD), Semi-Metallic (MX) and Carbon Based Friction (SX) formulation requirements for NEW technology on today’s vehicle platforms!