Symptom Chart

Failure of a mechanical brake component may not cause the yellow ABS warning indicator to illuminate or a DTC to be stored. The Symptom Chart is a starting point to begin diagnosis of these concerns.

SYMPTOM CHART

Condition	Possible Sources	Action
ABS false activation	Rear axle speed sensor ring is damaged	REMOVE the rear axle speed sensor from the differential housing. INSPECT the rear axle speed sensor.
	Front wheel speed sensor ring is damaged	INSPECT for damaged teeth. INSPECT both front wheel speed sensor rings.
	Sensor output is out of sync	If the left front sensor output is out of sync, Go to PINPOINT TEST C . If the right front sensor output is out of sync, Go to PINPOINT TEST E . If the rear sensor output is out of sync, Go to PINPOINT TEST G .
	Intermittent open or shorted wheel speed sensor circuit	Refer to Intermittent Failures to test circuits 514 (YE/RD), 516 (YE/BK), 523 (RD/PK), and 519 (LG/BK).
	Chafed wire insulation or pinched wire due to incorrect routing causing intermittent short	INSPECT the wiring harness from the front wheel knuckle to the frame and from the rear axle to the frame for worn or chafed wire insulation.
	Parking brake adjustment too tight	ELIMINATE the base brake system as the cause of the problem.
	Brake linings are grabby
	Loose wheel speed sensor(s)	TIGHTEN the wheel speed sensor bolt to specifications. REFER to SPECIFICATIONS in this article.
Wheels lock up	ABS outlet (dump) valve	Go to PINPOINT TEST A .
	Leaky ABS inlet (isolation) valve during ABS (soft)	ELIMINATE the base brake system as the cause of the problem. REFER to BRAKE SYSTEM-GENERAL INFORMATION .
	Damp or contaminated rear brake linings, or stuck/leaking rear disc brake caliper
	Binding parking brake
	Leaking rear axle seal
Yellow ABS warning indicator does not self check	Circuitry	Go to PINPOINT TEST P .
Yellow ABS warning indicator does not self check	Anti-lock brake system (ABS) module	Go to PINPOINT TEST P .
Hard or soft brake pedal	Stuck ABS inlet (isolation) valve (hard brake pedal) or leaky ABS outlet (dump) valve (soft brake pedal)	Go to PINPOINT TEST H .
	Hydraulic leak in brake line or hose, fitting, master cylinder, or caliper (soft brake pedal)	ELIMINATE the base brake system as the cause of the problem. REFER to BRAKE SYSTEM-GENERAL INFORMATION .
	Air in brake system (soft brake pedal)
	Little or no power assist (hard brake pedal)
	Stuck or inoperative or caliper (hard brake pedal)
	Pinched or crimped brake line or hose (hard brake pedal)
Lack of deceleration during medium/hard brake application	Stuck shut ABS inlet (isolation) valve or leaky ABS outlet (dump) valve (rear axle only)	Go to PINPOINT TEST H .
	Hydraulic leak in brake line or hose, fitting, master cylinder, or caliper	ELIMINATE the base brake system as the cause of the problem. REFER to BRAKE SYSTEM-GENERAL INFORMATION .
	Air in brake system
	Little or no power assist
	Stuck or inoperative caliper
	Ineffective brake linings
Vehicle pulls during braking	Frozen or binding caliper (one side of vehicle)	ELIMINATE the base brake system as the cause of the problem. REFER to BRAKE SYSTEM-GENERAL INFORMATION .
	Uneven brake lining wear
	Pinched or crimped brake line or hose
	Fully or partially blocked front ABS inlet (isolation) valve	INSTALL a new hydraulic control unit (HCU). REFER to HYDRAULIC CONTROL UNIT (HCU) in this article.
	Alignment	REFER to SUSPENSION SYSTEM-GENERAL INFORMATION .
	Front suspension	REFER to FRONT SUSPENSION - 4X2 or FRONT SUSPENSION - 4X4 .
	Rear suspension	REFER to REAR SUSPENSION .
	Steering components	REFER to STEERING LINKAGE .
Yellow ABS warning indicator on with system pass	Yellow ABS warning indicator circuit	DISCONNECT 25-pin connector C135 from the ABS module. Using a jumper wire, GROUND pin 15, circuit 603 (DG). If the lamp is off, INSTALL a new ABS module. REFER to ANTI-LOCK BRAKE SYSTEM (ABS) MODULE in this article. If the warning lamp remains on, REPAIR circuit 603 (DG).
Yellow ABS warning indicator on with system pass	ABS warning lamp circuit open
Soft or excessive pedal travel	Hydraulic leak in brake line or hose, fitting, master cylinder, or caliper	ELIMINATE the base brake system as the cause of the problem. REFER to BRAKE SYSTEM-GENERAL INFORMATION .
	Air in brake system
	Hydraulic control unit (HCU)	Go to PINPOINT TEST H .
No communication with the anti-lock brake control module	Fuse(s)	Go to PINPOINT TEST L .
	Circuitry
	Module