C1011 Left Front Wheel Speed Sensor Signal Erratic Performance

C1011 Left Front Wheel Speed Sensor Signal Erratic Performance - When the Left Front Wheel Speed Sensor (WSS) signal is intermittently missing while vehicle speed is above 25 mph (40 km/h) or erratic wheel speed signal during acceleration or sensed wheel speed is different from other wheel.

Possible Causes C1011

• Left front WSS loose circuit/connector/terminal damage.
• Left front tone wheel damage.
• Left front wheel/bearing damage.
• Improper left front tire pressure/mismatched tires.
• Left front WSS.
• Antilock Brake System (ABS) Module.

Diagnose C1011 Left Front Wheel Speed Sensor Signal Erratic Performance

Step 1. Check for DTC C1011 Code

This DTC must be active for the results of this test to be valid.

If DTC C100A LEFT FRONT WHEEL SPEED SENSOR CIRCUIT is present it must be repaired before continuing.

Turn the ignition on, with the scan tool erase DTC.

Caution: Make sure braking capability is available before road testing.

Road test the vehicle over 25 mph (40 km/h). Vehicle must be driven above 25 mph (40 km/h) for set conditions to be met. With the scan tool, read DTC.

Does the scan tool display DTC C1011 Code? 

YES, go to step 3.

NO, go to step 2.

Step 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. If graph shows periodic dropouts pay close attention to the tone wheel. Slowly accelerate as staright as possible from a stop to 25 mph (40 km/h)

Is the left front 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.

Step 3. Check for improper left front tire pressure/mismatched tires

Turn the ignition off, check and adjust the left front tire pressure. Check and adjust all other tire pressures, inspect for mismatched tires on vehicle.

Is the left front tire improperly inflated or mismatched tires on vehicle?

YES, repair as necessary.

NO, go to step 4.

Step 4. Check left front WSS looseness, inspect circuits/terminals for damage

Check all terminals for broken, bent, pushed out, or corroded terminals.

Inspect the Antilock Brake System module harness connector, left fron WSS , and left front WSS harness connector. Inspect the left front WSS for looseness, excessive corrosion and not properly fastened. Inspect the left front WSS signal and left front WSS supply circuits between the left front WSS and Antilock Brake System Module for damage.

Is the left front WSS loose or any of the wiring/connectors/terminals damaged?

YES, repair as necessary.

NO, go to step 5.

Step 5. Check left front wheel speed sensor for damage

Remove the left front wheel speed sensor, inspect the left front wheel speed sensor face for damage.

Is the left front WSS damaged?

YES, replace sensor and hub assembly.

NO, go to step 6.

Step 6. Check left front tone wheel/bearing for damage

Inspect the left front tone wheel/bearing for damage, missing teeth, cracks, corrosion or looseness. The tone wheel teeth should be perfectly square, not bent, or nicked.

Is the left front tone wheel/bearing damaged?

YES, repair as necessary.

NO, go to step 7.

Step 7. Check left front wheel bearing for damage

Inspect the left front wheel bearing for excessive runout or clearance. Refer to the appropriate service information, if necessary, for procedures or specifications

Is the left front wheel bearing damaged?

YES, repair as necessary.

NO, go to step 8.

Step 8. Left front wheel speed sensor

Replace the left front wheel speed sensor. Road test the vehicle over 25 mph (40 km/h). Vehicle must be driven above 25 mph (40 km/h) for set conditions to be met. With the scan tool, read ABS DTC.

Did DTC C1011 Code reset?

YES, replace the Antilock Brake System (ABS) Module. Perform the ABS Verification Test.

NO, test complete for DTC C1011 Left Front Wheel Speed Sensor Signal Erratic Performance

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