Diagnostic Test

CHECK FOR DTC C1027-LEFT REAR WHEEL SPEED SENSOR SIGNAL ERRATIC PERFORMANCE
NOTE: This DTC must be active for the results of this test to be valid.
1. Turn the ignition on.
2. With the scan tool, record and erase DTCs.
  CAUTION: Make sure brake capability is available before road testing.
3. Road test the vehicle over 25 mph (40 km/h).
  NOTE: Vehicle must be driven above 25 mph (40 km/h) for set conditions to be met.
4. With the scan tool, read DTCs.
  Does the scan tool display: C1027-LEFT REAR WHEEL SPEED SENSOR SIGNAL ERRATIC PERFORMANCE active?
  
  Yes
  - Go to step 3
  No
  - Go to step 2
CHECK WHEEL SPEED SENSOR SIGNALS
1. Turn the ignition on.
2. With the scan tool, monitor and graph ALL the WSS speeds and compare graph while an assistant drives the vehicle.
  NOTE: If graph shows periodic dropouts pay close attention to the tone wheel.
3. Slowly accelerate as straight as possible from a stop to 25 mph (40 km/h).
  Is the Left Rear WSS speed showing 0 mph (0 km/h) or not matching other wheels or showing erratic behavior?
  
  Yes
  - Go to step 3
  No
  - Perform the ABS-INTERMITTENT CONDITION diagnostic procedure. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .
CHECK FOR IMPROPER LEFT REAR TIRE PRESSURE/MISMATCHED TIRES
1. Turn the ignition off.
2. Check and adjust the Left Rear Tire pressure.
3. Check and adjust all other tire pressures.
4. Inspect for mismatched tires on vehicle.
  Is the Left Rear Tire improperly inflated or mismatched tires on vehicle?
  
  Yes
  - Repair as necessary.
  - Perform the ABS VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .
  No
  - Go to step 4
CHECK AXLE SHAFT FASTENER HARDWARE FOR LOOSENESS
1. Inspect the axle shaft fastener for looseness, and not properly fastened. Tighten fastener to proper specification as required.
  Was the Axle Shaft fastener loose?
  
  Yes
  - Repair as necessary.
  No
  - Go to step 5
CHECK LEFT REAR WSS LOOSENESS, INSPECT B3, B4 CIRCUITS/TERMINALS FOR DAMAGE
NOTE: Check all terminals for broken, bent, pushed out, or corroded terminals
1. Inspect the Anti-Lock Brake Module harness connector, Left Rear WSS, and Left Rear WSS harness connector
2. Inspect the Left Rear WSS for looseness, excessive corrosion and not properly fastened.
3. 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?
  
  Yes
  - Repair as necessary.
  - Perform the ABS VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .
  No
  - Go to step 6
CHECK LEFT REAR WHEEL SPEED SENSOR FOR DAMAGE
1. Remove the Left Rear Wheel Speed Sensor
2. Inspect the Left Rear Wheel Speed Sensor face for damage.
  Is the Left Rear Wheel Speed Sensor damaged?
  
  Yes
  - Replace sensor and hub assembly.
  - Perform the ABS VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .
  No
  - Go to step 7
CHECK LEFT REAR TONE WHEEL FOR DAMAGE
1. Inspect the Left Rear Tone Wheel for damage, missing teeth, cracks, corrosion or looseness.
  NOTE: The Tone Wheel teeth should be perfectly square, not bent, or nicked.
  
  Is the Left Rear Tone Wheel damaged?
  
  Yes
  - Repair as necessary.
  - Perform the ABS VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .
  No
  - Go to step 8
CHECK LEFT REAR WHEEL BEARING FOR DAMAGE
1. Inspect the Left Rear wheel bearing for excessive runout or clearance.
  NOTE: Refer to the appropriate service information, if necessary, for procedures or specifications.
  
  Is the Left Rear Wheel Bearing Damaged?
  
  Yes
  - Repair as necessary.
  - Perform the ABS VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .
  No
  - Go to step 9
LEFT REAR WHEEL SPEED SENSOR
1. Replace the Left Rear Wheel Speed Sensor in accordance with the Service Information.
2. Perform the ABS VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .
3. Road test the vehicle over 25 mph (40 km/h).
  NOTE: Vehicle must be driven above 25 mph (40 km/h) for set conditions to be met.
4. With the scan tool, read ABS DTCs.
  Did DTC C1027-LEFT REAR WHEEL SPEED SENSOR SIGNAL ERRATIC PERFORMANCE reset?
  
  Yes
  - Replace the Anti-Lock Brake Module in accordance with the Service Information.
  - Perform the ABS VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .
  No
  - Test complete.