For a complete wiring diagram Refer to Section 8W.When Monitored:With the ignition on.Set Condition:When the Left Rear Wheel Speed Sensor (WSS) Signal is intermittently missing while vehicle speed is above 40 km/h (25 mph) or erratic wheel speed signal during acceleration or sensed wheel speed is different from other wheels.Possible CausesLEFT REAR WSS LOOSE — B3, B4 CIRCUITS/CONNECTOR/TERMINAL DAMAGELEFT REAR TONE WHEEL DAMAGELEFT REAR WHEEL BEARING DAMAGEIMPROPER LEFT REAR TIRE PRESSURE/MISMATCHED TIRESLEFT REAR WSSANTI-LOCK BRAKE MODULE1. CHECK FOR DTC C1027-LEFT REAR WHEEL SPEED SENSOR SIGNAL ERRATIC PERFORMANCEThis DTC must be active for the results of this test to be valid.Turn the ignition on.With the scan tool, record and erase DTCs.Road test the vehicle over 40 km/h (25 mph).Vehicle must be driven above 40 km/h (25 mph) for set conditions to be met.With the scan tool, read DTCs.Does the scan tool display: C1027-LEFT REAR WHEEL SPEED SENSOR SIGNAL ERRATIC PERFORMANCE active?YesGo To 3NoGo To 22. CHECK WHEEL SPEED SENSOR SIGNALSTurn the ignition on.With the scan tool, monitor and graph ALL the WSS speeds and compare graph while an assistant drives the vehicle.If graph shows periodic dropouts pay close attention to the tone wheel.Slowly accelerate as straight as possible from a stop to 40 km/h (25 mph).Is the Left Rear WSS speed showing 0 km/h (0 mph) or not matching other wheels or showing erratic behavior?YesGo To 3 NoRefer to the ABS-INTERMITTENT CONDITION TEST. (Refer to 5 - BRAKES - DIAGNOSIS AND TESTING)3. CHECK FOR IMPROPER LEFT REAR TIRE PRESSURE/MISMATCHED TIRESTurn the ignition off.Check and adjust the Left Rear Tire pressure.Check and adjust all other tire pressures.Inspect for mismatched tires on vehicle.Is the Left Rear Tire improperly inflated or mismatched tires on vehicle?YesRepair as necessary.Perform ABS VERIFICATION TEST. (Refer to 5 - BRAKES - STANDARD PROCEDURE)NoGo To 44. CHECK LEFT REAR WSS LOOSENESS, INSPECT B4, B5 CIRCUITS/TERMINALS FOR DAMAGECheck all terminals for broken, bent, pushed out, or corroded terminalsInspect the Anti-Lock Brake Module harness connector, Left Rear WSS, and Left Rear WSS harness connectorInspect the Left Rear WSS for looseness, excessive corrosion and not properly fastened.Inspect the (B3) Left Rear WSS Signal and (B4) Left Rear WSS Supply circuits between the Left Rear WSS and Anti-Lock Brake Module for damage.Is the Left Rear WSS loose or any of the wiring/connectors/terminals damaged?YesRepair as necessary.Perform ABS VERIFICATION TEST. (Refer to 5 - BRAKES - STANDARD PROCEDURE)NoGo To 55. CHECK LEFT REAR WHEEL SPEED SENSOR FOR DAMAGERemove the Left Rear Wheel Speed SensorInspect the Left Rear Wheel Speed Sensor face for damage. Is the Left Rear Wheel Speed Sensor damaged?YesReplace sensor and hub assembly.Perform ABS VERIFICATION TEST. (Refer to 5 - BRAKES - STANDARD PROCEDURE)NoGo To 66. CHECK LEFT REAR TONE WHEEL FOR DAMAGEInspect the Left Rear Tone Wheel for damage, missing teeth, cracks, corrosion or looseness.The Tone Wheel teeth should be perfectly square, not bent, or nicked.Is the Left Rear Tone Wheel damaged?YesRepair as necessary.Perform ABS VERIFICATION TEST. (Refer to 5 - BRAKES - STANDARD PROCEDURE)NoGo To 77. CHECK LEFT REAR WHEEL BEARING FOR DAMAGEInspect the Left Rear wheel bearing for excessive runout or clearance.Refer to the appropriate service information, if necessary, for procedures or specifications.Is the Left Rear Wheel Bearing Damaged?YesRepair as necessary.Perform ABS VERIFICATION TEST. (Refer to 5 - BRAKES - STANDARD PROCEDURE)NoGo To 88. LEFT REAR WHEEL SPEED SENSORReplace the Left Rear Wheel Speed Sensor in accordance with the Service Information.Perform ABS VERIFICATION TEST. (Refer to 5 - BRAKES - STANDARD PROCEDURE)Road test the vehicle over 40 km/h (25 mph).Vehicle must be driven above 40 km/h (25 mph) for set conditions to be met.With the scan tool, read ABS DTCs.Did DTC C1027-LEFT REAR WHEEL SPEED SENSOR SIGNAL ERRATIC PERFORMANCE reset?YesReplace the Anti-Lock Brakes Module in accordance with the Service Information.Perform ABS VERIFICATION TEST. (Refer to 5 - BRAKES - STANDARD PROCEDURE)NoTest Complete.