C1027
C1027 - Left Rear Wheel Speed Sensor Signal Erratic Performance
For a complete wiring diagram, refer to ,.
• When Monitored: With the ignition ON.
• Set Condition: When the left rear wheel speed sensor signal is intermittently missing while vehicle speed is more than 40 km/h (25 m.p.h.) or erratic wheel speed signal during acceleration or sensed wheel speed is different from other wheels.
Test Step 1 - Test for DTC C1027 - Left Rear Wheel Speed Sensor Signal Erratic Performance
• 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.
Ensure brake capability is available before road testing.
• Road test the vehicle over 40 km/h (25 m.p.h.).
• Vehicle must be driven more than 40 km/h (25 m.p.h.) 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 Test Step 3 => [ Test Step 3 - Test for Improper Left Rear Tire Pressure/Mismatched
Tires ]
No
• Go to Test Step 2 => [ Test Step 2 - Test Wheel Speed Sensor Signals ]
Test Step 2 - Test 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.
• 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 m.p.h.).
Is the left rear WSS speed showing 0 km/h (0 m.p.h.) or not matching other wheels or showing erratic behavior?
Yes
• Go to Test Step 3 => [ Test Step 3 - Test for Improper Left Rear Tire Pressure/Mismatched
Tires ]
No
• Perform the ABS Intermittent Condition Test. Refer to => Non-DTC Based Diagnostics. ABS Intermittent Condition Test
Test Step 3 - Test for Improper Left Rear Tire Pressure/Mismatched Tires
• Turn the ignition OFF.
• Test and adjust the left rear tire pressure.
• Test 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. Refer to => Non-DTC
Based Diagnostics. ABS Verification Test
No
• Go to Test Step 4 => [ Test Step 4 - Test Axle Shaft Fastener Hardware for Looseness ]
Test Step 4 - Test Axle Shaft Fastener Hardware for Looseness
• 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 Test Step 5 => [ Test Step 5 - Test Left Rear WSS Looseness, Inspect Circuits/Terminals
for Damage ]
Test Step 5 - Test Left Rear WSS Looseness, Inspect Circuits/Terminals for Damage
• Test 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 left rear WSS signal and 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. Refer to => Non-DTC
Based Diagnostics. ABS Verification Test
No
• Go to Test Step 6 => [ Test Step 6 - Test Left Rear Wheel Speed Sensor for Damage ]
Test Step 6 - Test 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. Refer to => Non-DTC
Based Diagnostics. ABS Verification Test
No
• Go to Test Step 7 => [ Test Step 7 - Test Left Rear Tone Wheel for Damage ]
Test Step 7 - Test Left Rear Tone Wheel for Damage
• Inspect 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?
Yes
• Repair as necessary.
• Perform ABS Verification Test. Refer to => Non-DTC
Based Diagnostics. ABS Verification Test
No
• Go to Test Step 8 => [ Test Step 8 - Test Left Rear Wheel Bearing for Damage ]
Test Step 8 - Test Left Rear Wheel Bearing for Damage
• Inspect 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?
Yes
• Repair as necessary.
• Perform ABS Verification Test. Refer to => Non-DTC
Based Diagnostics. ABS Verification Test
No
• Go to Test Step 9 => [ Test Step 9 - Left Rear Wheel Speed Sensor ]
Test Step 9 - Left Rear Wheel Speed Sensor
• Replace the left rear wheel speed sensor.
• Perform ABS Verification Test. Refer to => Non-DTC
Based Diagnostics. ABS Verification Test
• Road test the vehicle over 40 km/h (25 m.p.h.).
• Vehicle must be driven more than 40 km/h (25 m.p.h.) 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. Refer to => Non-DTC
Based Diagnostics. ABS Verification Test
No
• Test Complete.
• Perform ABS Verification Test. Refer to => Non-DTC
Based Diagnostics. ABS Verification Test