Symptom Chart

NOTE: 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.

NOTE: Refer to Wiring Diagrams for connector numbers stated in PINPOINT TESTS .

SYMPTOM

Condition	Possible Sources	Action
No communication with the anti-lock brake system (ABS) module	Battery junction box (BJB) fuses 102 (40A), 101 (40A), fuse junction panel fuse 10 (10A). Circuitry. ABS Module.	Go To PINPOINT TEST A: NO COMMUNICATION WITH THE ANTI-LOCK BRAKE CONTROL MODULE .
Unable to enter selftest	Anti-lock brake system (ABS) module.	Go To PINPOINT TEST B: UNABLE TO ENTER SELF-TEST .
ABS false activation, ABS too sensitive, ABS activates on normal stop	Front wheel speed sensor indicator is damaged. Rear axle speed sensor indicator is damaged.	INSPECT for damaged teeth on the wheel speed sensor indicator. INSPECT both front and rear axle speed sensor indicators.
	Loose sensor(s).	TIGHTEN sensor bolt to specifications. REFER to SPECIFICATIONS .
	Sensor output is erratic.	Go To PINPOINT TEST J: DTCs C1233 LF, C1234 RF, C1235 RR, C1236 LR, C1222 - ANTI-LOCK BRAKE SENSOR SIGNAL MISSING OR ERRATIC, WHEEL SPEED MISMATCH .
	Intermittent open or shorted sensor circuit.	Go To PINPOINT TEST G: DTC C1145 RF, C1155 LF, C1165 RR, C1175 LR - ANTI-LOCK BRAKE SENSOR INPUT FAILURE .
	Chafed wire insulation or pinched wire due to incorrect routing causing intermittent short.	INSPECT wiring harness from front sensor at knuckle to the frame and from the rear axle to the frame for worn or chafed wire insulation.
Wheels lock up - with no ABS warning indicator lamp	Leaky inlet (isolation) valve during ABS (soft). Damp or contaminated rear brake linings, or stuck/leaking rear disc brake caliper. Binding parking brake.	ELIMINATE base brake system as cause of problem. REFER to BRAKE SYSTEM-GENERAL INFORMATION .
Hard or soft brake pedal	Leaky outlet (dump) valve (soft brake pedal).	Go To PINPOINT TEST K: SOFT OR EXCESSIVE PEDAL TRAVEL .
Hard or soft brake pedal	Hydraulic leak in brake line or hose, fitting, master cylinder, or caliper (soft brake pedal). Air in brake system (soft brake pedal). Little or no vacuum boost (hard brake pedal). Stuck or inoperative caliper (hard brake pedal). Pinched or crimped brake line or hose (hard brake pedal).	ELIMINATE base brake system as cause of problem. REFER to BRAKE SYSTEM-GENERAL INFORMATION .
Excessive pedal travel	Base brake system.	REFER to ANTI-LOCK CONTROL-TRACTION CONTROL & STABILITY .
Excessive pedal travel	Leaking dump valves in HCU.	Go To PINPOINT TEST K: SOFT OR EXCESSIVE PEDAL TRAVEL .
Lack of deceleration during medium/hard brake application	Leaky outlet (dump) valve (rear axle only).	Go To PINPOINT TEST K: SOFT OR EXCESSIVE PEDAL TRAVEL .
Lack of deceleration during medium/hard brake application	Hydraulic leak in brake line or hose, fitting, master cylinder, or caliper. Air in brake system. l Little or no vacuum boost. Stuck or inoperative caliper. Ineffective brake linings.	ELIMINATE base brake system as cause of problem. REFER to BRAKE SYSTEM-GENERAL INFORMATION .
Vehicle pulls during braking	Incorrectly adjusted rear brake.	ELIMINATE base brake system as cause of problem. REFER to BRAKE SYSTEM-GENERAL INFORMATION .
	Loose or worn steering or suspension components.	REFER to STEERING SYSTEM-GENERAL INFORMATION for steering or SUSPENSION SYSTEM-GENERAL INFORMATION for suspension..
	Leaky outlet (dump) valve (rear axle only).	Go To PINPOINT TEST K: SOFT OR EXCESSIVE PEDAL TRAVEL .
	Frozen or binding caliper (one side of vehicle). Uneven brake lining wear.	ELIMINATE base brake system as cause of problem. REFER to BRAKE SYSTEM-GENERAL INFORMATION .
	Vehicle out of alignment. Pinched or crimped brake line or hose.	REFER to SUSPENSION SYSTEM-GENERAL INFORMATION .
Yellow ABS warning indicator on with system pass	Yellow ABS warning indicator circuit. Anti-lock brake system (ABS) module.	REFER to INSTRUMENT CLUSTER .