Symptom Troubleshooting Chart - Anti-Lock Brake System (Abs)

SYMPTOM TROUBLESHOOTING CHART - ANTI-LOCK BRAKE SYSTEM (ABS)

Problem	Possible Cause	Action
No communication with the anti-lock brake system (ABS) module	Circuitry or connection in the international standards organization (ISO) 9141 network ABS module	See PINPOINT TEST 1: NO COMMUNICATION WITH THE ANTI-LOCK BRAKE SYSTEM (ABS) MODULE , .
Incorrectly adjusted rear brakes or brake shoe linings grab	Rear brake adjustment Rear brake shoe linings	See BRAKE SYSTEM DIAGNOSIS (CONVENTIONAL) , .
Base brake mechanical concern for wheels lockup	Rear brake shoe linings Wheel cylinder Rear brakes	See BRAKE SYSTEM DIAGNOSIS (CONVENTIONAL) , .
	Parking brake	See SYMPTOM TROUBLESHOOTING CHART - PARKING BRAKE , .
	Rear axle seal	See REAR DRIVE AXLE AND DIFFERENTIAL , .
Soft pedal/spongy pedal no warning indicator	Brake line, hose, fitting, master cylinder, wheel cylinder or caliper Air in the brake system	See BRAKE SYSTEM DIAGNOSIS (CONVENTIONAL) , .
Base brake mechanical concern (hard pedal)	Vacuum boost Wheel cylinder or caliper Brake line or hose	See BRAKE SYSTEM DIAGNOSIS (CONVENTIONAL) , .
Base brake hydraulic concern during medium/hard brake application	Brake line or hose, fitting, master cylinder, wheel cylinder or caliper Air in the brake system	See BRAKE SYSTEM DIAGNOSIS (CONVENTIONAL) , .
Base brake mechanical concern during medium/hard brake application	Vacuum boost Wheel cylinder or caliper Brake line or hose Brake shoe or pad linings	See BRAKE SYSTEM DIAGNOSIS (CONVENTIONAL) , .
Base brake mechanical concern for vehicle pulls	Rear brakes Caliper Brake pad or shoe wear	See BRAKE SYSTEM DIAGNOSIS (CONVENTIONAL) , .
Base brake hydraulic concern for vehicle pulls	Brake line or hose	See BRAKE SYSTEM DIAGNOSIS (CONVENTIONAL) , .
One wheel locks up; no DTCs t recorded	Caliper Wheel cylinder Brake pad/shoe linings	See BRAKE SYSTEM DIAGNOSIS (CONVENTIONAL) , .
One wheel locks up; no DTCs t recorded	Hydraulic control unit (HCU)	INSTALL a new HCU. see ANTI-LOCK BRAKE SYSTEM (ABS) MODULE .
The red brake warning indicator stays on when the ignition switch is in the RUN position	Circuitry Instrument cluster Anti-lock brake system (ABS) module	See INSTRUMENT CLUSTER in TROUBLESHOOTING (INSTRUMENT/DRIVER INFORMATION) - B-SERIES article.
The ABS warning indicator stays on when the ignition switch is in the RUN position	Circuitry Instrument cluster Anti-lock brake system (ABS) module	See INSTRUMENT CLUSTER in TROUBLESHOOTING (INSTRUMENT/DRIVER INFORMATION) - B-SERIES article.
The red brake warning indicator does not self-check	Circuitry Instrument cluster Anti-lock brake system (ABS) module	See INSTRUMENT CLUSTER in TROUBLESHOOTING (INSTRUMENT/DRIVER INFORMATION) - B-SERIES article.
The yellow ABS warning indicator does not self-check	Circuitry Instrument cluster Anti-lock brake system (ABS) module	See INSTRUMENT CLUSTER in TROUBLESHOOTING (INSTRUMENT/DRIVER INFORMATION) - B-SERIES article.
The yellow ABS warning indicator self-checks OK but automatically begins flashing	Circuitry Anti-lock brake system (ABS) module Hydraulic control unit (HCU)	Retrieve the DTCs and See ANTI-LOCK BRAKE SYSTEM (ABS) MODULE DIAGNOSTIC TROUBLE CODE (DTC) INDEX , .
Soft/hard/excessive brake pedal travel	Brake line, hose, fitting, master cylinder, wheel cylinder, wheel cylinder or caliper Air in the brake system	See BRAKE SYSTEM DIAGNOSIS (CONVENTIONAL) , .
Soft/hard/excessive brake pedal travel	HCU	Inspect the HCU for visible signs of leaking. If any leaks are present, repair or replace as necessary and bleed the brake system. See BRAKE SYSTEM BLEEDING .
The yellow ABS/red brake light always on, no DTCs	Circuitry Anti-lock brake system control (ABS) module	See INSTRUMENT CLUSTER in TROUBLESHOOTING (INSTRUMENT/DRIVER INFORMATION) - B-SERIES article.