ABS 5.3 Mode Two Pressure-Drop

The electronic control unit will activate the inlet solenoid valve of the affected wheel or wheels causing it to mechanically close, preventing the pressure from the master cylinder from reaching the brake caliper. The electronic control unit will also activate the outlet solenoid valve of the affected wheel or wheels causing it to mechanically open releasing the brake fluid pressure from the caliper, eliminating lock up.

The pressure is absorbed by the reservoir and the motor pump assembly will activate. This action will allow brake fluid flow to the damper chamber where some of the oscillations are removed; however some kickback will be felt at the brake pedal.

Mode Three Pressure-Hold

When the ideal wheelspeed is achieved the electronic control unit will activate the pressure-hold mode. The pump and motor assembly will continue to operate and the outlet solenoid will electronically turn off. This will cause the outlet solenoid valve to be mechanically closed. At this point the inlet and outlet solenoid valves are both closed and the remaining brake fluid pressure is retained in the caliper.

ABS 5.3 Mode Four Pressure-Increase

Pressure increase solenoid valve orientation is the same as normal braking. The only difference is that the pump and motor assembly are in operation, assisting the master cylinder in applying the affected caliper. The ABS 5.3 electronic control unit is located behind and to the right of the glove box. The cruise control unit has been moved to the driver side of the vehicle to make room for the ABS control unit. Warning: Remove the bolts securing the dash pad to the dash frame. Use minimum force to prevent damaging the dash pad.

ABS operation, self check and system diagnosis is a summary of the work performed by the ABS control unit. Self check, which is performed when the ignition is first turned on and when the vehicle speed has reached 3 mph with no brake applied and 8 mph if the brake has been applied, has been enhanced so that its operation is not objectionable to the customer.

The length of time in which the self check can be felt or heard has been reduced from 800 milliseconds to 200 milliseconds. If any problems are detected, this information will continue to be communicated to the operator through the ABS warning light, and as in previous model years, the ABS system will be passive (non-operational) with the warning light on.