C1143: Missing Tooth in Left Rear Tone Ring
The C1143 code is a manufacturer-specific fault indicating that the ABS control module has detected a missing or damaged tooth on the left rear wheel tone ring. The module monitors the voltage signal from the wheel speed sensor; if the signal shows a periodic interruption or irregularity at a specific point in each revolution, it determines that a tone ring tooth is absent. This prevents the ABS from accurately calculating wheel speed, potentially causing incorrect ABS activation or disabling traction and stability control systems.
1. Commonly Affected Makes
2. Most Common Causes
- Left rear tone ring broken, missing teeth, or severely corroded
- Left rear wheel speed sensor damaged or with out-of-spec internal resistance
- Metal debris or dirt buildup in the gap between the sensor and tone ring
- Left rear speed sensor wiring shorted, open, or with high resistance
- Left rear speed sensor connector with corroded or loose terminals
- Excessive play in the left rear wheel bearing altering sensor alignment
3. Symptoms You Will Notice
- ABS warning light illuminated
- Traction or stability control warning lights on
- ABS may activate unnecessarily or fail to engage
- Possible loss of traction or stability control functions
4. Step-by-Step Diagnosis
Scan for additional codes and verify C1143 is present
Inspect left rear tone ring for damage, missing teeth, or corrosion
Check left rear wheel speed sensor and its wiring for damage or contamination
Measure sensor resistance and compare to specifications
Check wheel bearing for excessive play that could affect sensor gap
5. Frequently Asked Questions
Is it safe to drive?▼
Driving is possible but not recommended, as ABS, traction control, and stability control may not function properly, increasing the risk of loss of control in emergency maneuvers or slippery conditions.
How much does it cost to fix?▼
Repair costs typically range from $200 to $600, depending on whether the tone ring, sensor, or wheel bearing needs replacement, and labor rates in your area.