Brake Assist System Diagnosis

WARNING: This page is about a different car, the 2003 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: This diagnostic table is designed to diagnose ONLY the components of the brake ASSIST system in order to determine if the brake ASSIST system is operating properly. You will be directed by the appropriate Symptom table to go to other brake system diagnostic tables as appropriate.

Perform HYDRAULIC BRAKE SYSTEM DIAGNOSTIC STARTING POINT .
Inspect for proper brake pedal travel. See BRAKE PEDAL TRAVEL MEASUREMENT & INSPECTION under ADJUSTMENTS & INSPECTIONS. Is the brake pedal travel distance within the acceptable limits? If so, go to step 5. If not, go to next step.
1. Inspect for worn, missing, misaligned, bent or damaged brake pedal system components.
  - For the brake pedal pushrod component inspection, see BRAKE PEDAL PUSHROD INSPECTION under ADJUSTMENTS & INSPECTIONS.
  - Inspect the brake pedal bushings for excessive wear and/or damage and inspect the brake pedal for a misaligned, bent and/or damaged condition.
2. Replace the brake pedal system components that are worn, missing, misaligned, bent or damaged. Refer to the following procedures as necessary.
  - See BRAKE PEDAL under REMOVAL & INSTALLATION.
  - For a bent or damaged pedal pushrod, replace power brake booster. See POWER BRAKE BOOSTER under REMOVAL & INSTALLATION.
Did you find and replace any worn, missing, misaligned, bent or damaged brake pedal system components? If so, go to next step. If not, go to step 5.
Reinspect for proper brake pedal travel. See BRAKE PEDAL TRAVEL MEASUREMENT & INSPECTION under ADJUSTMENTS & INSPECTIONS. Is the brake pedal travel distance within the acceptable limits? If so, go to step 8. If not, go to next step.
Check the engine vacuum source that supplies vacuum to the vacuum brake booster. See BRAKE SYSTEM VACUUM SOURCE TEST under SYSTEM TESTS. Is the vacuum reading within the acceptable limits? If so, go to next step. If not, go to BASIC DIAGNOSTIC PROCEDURES article in ENGINE PERFORMANCE.
During the vacuum source inspection in step 5, did the vacuum booster check valve operate properly? If so, go to step 8. If not, go to next step.
Replace the vacuum booster check valve. After replacement, go to next step.
1. Pump the brake pedal several times until the brake pedal effort increases significantly.
2. Maintain moderate foot pressure on the brake pedal and start the engine. Observe pedal operation.
Did the brake pedal drop slightly, then remain firm after the engine was started? If so, go to next step. If not, go to step 12.
- Release the brake pedal.
- Turn the ignition OFF, then wait 15 seconds.
- Pump the brake pedal 2 times to check for vacuum booster available vacuum reserve. Observe pedal effort. If operating properly, the vacuum brake booster should maintain assist for at least 2 pedal applications.
Did the brake pedal effort increase significantly? If so, go to step 12. If not, go to next step.
Inspect the brake pedal pushrod and the brake pedal for misalignment, a bent condition and/or damage. See BRAKE PEDAL PUSHROD INSPECTION under ADJUSTMENTS & INSPECTIONS. Is the brake pedal pushrod and/or the brake pedal misaligned, bent or damaged? If so, go to next step. If not, go to step 13.
If brake pedal pushrod is bent or damaged, see POWER BRAKE BOOSTER under REMOVAL & INSTALLATION. If brake pedal is bent or damaged, see BRAKE PEDAL under REMOVAL & INSTALLATION.
Replace power brake booster. See POWER BRAKE BOOSTER under REMOVAL & INSTALLATION. After repairs are complete, go to next step.
Install or connect any components that were removed or disconnected during diagnosis