C1027
C1027-LEFT REAR WHEEL SPEED SENSOR SIGNAL ERRATIC PERFORMANCE
For a complete wiring diagram Refer to Diagrams/Electrical. Electrical Diagrams
- 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.
Diagnostic Test
1. 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.
Turn the ignition on.
With the scan tool, record and erase DTCs.
Road test the vehicle over 40 km/h (25 mph).
NOTE: 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?
Yes
- Go To 3
No
- Go To 2
2. CHECK WHEEL SPEED SENSOR SIGNALS
Turn the ignition on.
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.
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?
Yes
- Go To 3
No
- Refer to the ABS-INTERMITTENT CONDITION TEST. ABS Intermittent Condition Test
3. CHECK FOR IMPROPER LEFT REAR TIRE PRESSURE/MISMATCHED TIRES
Turn 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?
Yes
- Repair as necessary.
- Perform ABS VERIFICATION TEST. ABS Verification Test
No
- Go To 4
4. CHECK LEFT REAR WSS LOOSENESS, INSPECT B4, B5 CIRCUITS/TERMINALS FOR DAMAGE
NOTE: Check all terminals for broken, bent, pushed out, or corroded terminals
Inspect the Anti-Lock Brake Module harness connector, Left Rear WSS, and Left Rear WSS harness connector
Inspect 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?
Yes
- Repair as necessary.
- Perform ABS VERIFICATION TEST. ABS Verification Test
No
- Go To 5
5. CHECK LEFT REAR WHEEL SPEED SENSOR FOR DAMAGE
Remove the Left Rear Wheel Speed Sensor
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 ABS VERIFICATION TEST. ABS Verification Test
No
- Go To 6
6. CHECK LEFT REAR TONE WHEEL FOR DAMAGE
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 ABS VERIFICATION TEST. ABS Verification Test
No
- Go To 7
7. CHECK LEFT REAR WHEEL BEARING FOR DAMAGE
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 ABS VERIFICATION TEST. ABS Verification Test
No
- Go To 8
8. LEFT REAR WHEEL SPEED SENSOR
Replace the Left Rear Wheel Speed Sensor.
Perform ABS VERIFICATION TEST. ABS Verification Test
Road test the vehicle over 40 km/h (25 mph).
NOTE: 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?
Yes
- Replace the Anti-Lock Brakes Module.
- Perform ABS VERIFICATION TEST. ABS Verification Test
No
- Test Complete.