What Does C1143 Mean?
This code indicates the ABS control module has detected a missing tooth fault on the left rear wheel speed sensor tone ring. The module has identified a waveform irregularity from the LR sensor consistent with physical damage to the reluctor ring. The left rear tone ring may be pressed onto the axle shaft or integrated into the wheel bearing hub assembly.
Safety Warning
ABS and traction control are likely disabled. Left rear wheel speed monitoring is compromised. Repair promptly to restore full ABS capability.
Common Causes
40%
Cracked or broken left rear tone ring with missing teeth from corrosion exposure and road salt damage
25%
Heavy corrosion buildup on tone ring teeth creating uneven signal patterns
20%
Excessive wheel bearing play causing variable air gap between sensor and tone ring
15%
Metallic contamination on sensor magnetic element from brake dust or gear oil
Diagnostic Steps
1
Step 1: Raise the vehicle, remove the left rear wheel, and inspect the tone ring. On rear axle vehicles, this may require removing the brake drum or rotor to access the ring on the axle shaft.
2
Step 2: Rotate the axle/hub slowly and inspect every tooth around the full circumference for cracks, chips, missing sections, or heavy corrosion.
3
Step 3: Clean the tone ring and sensor tip. Measure the air gap with a feeler gauge and compare to specifications.
4
Step 4: Connect an oscilloscope to the LR speed sensor and rotate the wheel. Verify even spacing between signal peaks. An abnormal gap indicates the damaged tooth location.
5
Step 5: Replace the tone ring (or axle shaft/hub assembly if integrated), clear codes, and test drive verifying stable LR wheel speed data above 15 mph.
Estimated Repair Cost
$150 - $550
Parts + labor, varies by vehicle and location
This code indicates the ABS control module has detected a missing tooth fault on the left rear wheel speed sensor tone ring. The module has identified a waveform irregularity from the LR sensor consistent with physical damage to the reluctor ring. The left rear tone ring may be pressed onto the axle...
The most common cause of C1143 (Wheel Speed Sensor LR Tone Ring Tooth Missing Fault) is: Cracked or broken left rear tone ring with missing teeth from corrosion exposure and road salt damage
Typical repair costs for C1143 range from $150 to $550, depending on the vehicle, location, and whether you do it yourself or go to a shop.
ABS and traction control are likely disabled. Left rear wheel speed monitoring is compromised. Repair promptly to restore full ABS capability.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1143 to identify the root cause.
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Quick Info
Category
Chassis
System
Anti-lock Brake System (ABS) / Traction Control System
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