Symptom Chart

SYMPTOM CHART

Condition	Possible Sources	Action
No communication with the anti-lock brake system (ABS) module	Circuitry ABS module	REFER to MODULE COMMUNICATIONS NETWORK article to diagnose the no communication concern.
Soft/excessive brake pedal travel	Inlet (isolation) valve or hydraulic outlet (dump) valve Leaky inlet (isolation) valve during ABS applications (soft)	Go to Pinpoint Test F .
	Brake line or hose, fitting, master cylinder, wheel cylinder or caliper Air in brake system Brake shoe or pad linings Parking brake Rear axle seal	ELIMINATE the base brake system as the cause of the problem. REFER to BRAKE SYSTEM - GENERAL INFORMATION .
ABS false activation, ABS too sensitive, ABS activates on normal stop	Front anti-lock brake sensor indicators	INSPECT both front wheel speed sensor rings for damaged teeth. CHECK the wheel speed sensor gap.
	Chafed wire insulation or pinched wire	INSPECT the wiring harness from the front wheel speed sensor knuckle to the frame and from the rear axle to the frame.
	Open or shorted wheel speed sensor circuit	Go to Pinpoint Test A .
	Rear wheel speed sensor indicator	INSPECT the rear ABS indicator.
	Wheel speed sensor	Go to Pinpoint Test C .
	Rear brake adjustment Linings	ELIMINATE the base brake system as the cause of the problem. REFER to BRAKE SYSTEM - GENERAL INFORMATION .
Wheels lock up	Hydraulic outlet (dump) valve Leaky inlet (isolation) valve during ABS (soft)	Go to Pinpoint Test F .
	Front or rear brakes Parking brake Rear axle seal	ELIMINATE the base brake system as the cause of the problem. REFER to BRAKE SYSTEM - GENERAL INFORMATION .
Vehicle pulls during braking	Sensor failure	Go to Pinpoint Test A .
	Base brake system	ELIMINATE the base brake system as the cause of the problem. REFER to BRAKE SYSTEM - GENERAL INFORMATION .
Anti-lock brake system (ABS) warning indicator illuminated	Circuitry Brake fluid level ABS module	REFER to INSTRUMENT CLUSTER to continue diagnosis on the warning indicator.
The red BRAKE warning indicator stays on when the ignition switch is in RUN	Circuitry Brake fluid level Instrument cluster ABS module	REFER to BRAKE SYSTEM - GENERAL INFORMATION for diagnosis of the red BRAKE warning indicator is always on.
The yellow anti-lock brake system (ABS) warning indicator does not self-check	Circuitry Brake fluid level Instrument cluster ABS module	REFER to INSTRUMENT CLUSTER to continue diagnosis of the warning indicator.