General Diagnostic Table: Inspection

WARNING: This page is about a different car, the 2022 Subaru WRX. However, it is still accessible from the selected car via links, so may be relevant.

GENERAL DIAGNOSTIC AND SYMPTOMS DESCRIPTION

Symptoms	Possible cause	Corrective action
Insufficient braking	(1) Brake fluid leakage from the hydraulic mechanism	Repair or replace (cup, piston seal, piston boot, master cylinder piston kit, brake pipe or brake hose).
	(2) Entry of air into the hydraulic mechanism	Bleed air.
	(3) Wear, deteriorated surface material, water or brake fluid on pad or lining	Replace, grind or clean.
	(4) Improper operation of master cylinder assembly, brake caliper, vacuum booster assembly or check valve	Repair or replace.
Unstable or uneven braking	(1) Brake fluid on pad surface, lining surface, or brake disc	Correct the cause of brake fluid leakage, and clean or replace.
	(2) Defective brake disc	Repair or replace the brake disc.
	(3) Improper pad or lining contact, deteriorated surface, deteriorated or worn material	Repair by grinding, or replace.
	(4) Deformed brake back plate	Repair or replace.
	(5) Overinflation of tires	Adjust to the specified air pressure.
	(6) Defective wheel alignment	Adjust alignment.
	(7) Loose brake back plate or support installation bolt	Tighten to the specified torque.
	(8) Defective hub unit bearing	Replace.
	(9) Defective hydraulic system	Replace the cylinder, brake pipe or brake hose.
	(10) Unstable performance of the parking brake	Check, adjust or replace the rear brake and cable system.
Excessive pedal stroke	(1) Entry of air into the hydraulic mechanism	Bleed air.
	(2) Excessive play in the master cylinder push rod	Adjust.
	(3) Brake fluid leakage from the hydraulic mechanism	Repair or replace (cup, piston seal, piston boot, master cylinder piston kit, brake pipe or brake hose).
	(4) Improper pad or lining contact or wear	Repair or replace.
Brake dragging or improper brake return	(1) Insufficient pedal play	Adjust play.
	(2) Improper master cylinder return	Clean or replace the cylinder.
	(3) Clogged hydraulic system	Replace.
	(4) Improper return or adjustment of parking brake	Repair or adjust.
	(5) Weakened spring tension or breakage of shoe return spring	Replace the spring.
	(6) Improper brake caliper operation	Repair or replace.
	(7) Defective hub unit bearing	Replace.
Brake noise (creaking sound)	(1) Hardened or deteriorated brake pad	Replace the brake pad.
	(2) Worn brake pad	Replace the brake pad.
	(3) Loose brake back plate or support installation bolt	Tighten to the specified torque.
	(4) Loose hub unit bearing	Tighten to the specified torque.
	(5) Dirt on brake disc	Clean the brake disc. Clean or replace brake assembly.
Brake noise (hissing sound)	(1) Worn brake pad	Replace the brake pad.
	(2) Improperly installed brake pad	Correct or replace the brake pad.
	(3) Loose or bent brake disc	Retighten or replace.
Brake noise (click sound)	Excessively worn brake pad or support	Replace the brake pad or the support.
VDC warning light or EyeSight warning light illuminating	(1) Stop light switch adjustment malfunction	Adjust the stop light switch. Ref. to BRAKE>STOP LIGHT SWITCH>ADJUSTMENT>ADJUSTMENT WHEN VDC WARNING LIGHT OR EYESIGHT WARNING LIGHT IS ILLUMINATING .
	(2) VDC system failure	Check the VDC system. Ref. to BRAKE CONTROL (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .
	(3) EyeSight system failure	Check the EyeSight system. Ref. to EYESIGHT (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .
Stop light illuminating due to vibrations, etc. during driving (brake operation not performed)	Stop light switch adjustment malfunction	Adjust the stop light switch. Ref. to BRAKE>STOP LIGHT SWITCH>ADJUSTMENT>ADJUSTMENT WHEN VDC WARNING LIGHT OR EYESIGHT WARNING LIGHT IS ILLUMINATING .