Wheel Speed Sensor LR Tone Ring Tooth Missing Fault
The ABS system detected that a tooth is missing from the toothed ring (tone ring) on your left rear wheel, which is like a car's odometer skipping numbers—the sensor can't read speed properly. This causes the ABS module to lose confidence in that wheel's speed data.
The ABS ECU monitors the tone ring's tooth pattern as it passes the wheel speed sensor. It counts tooth intervals and expects a consistent pattern; if teeth are missing or damaged, the sensor signal shows irregular gaps. The ECU detects this anomaly when pulse intervals exceed normal thresholds.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Tooth pulse interval consistency | Regular, evenly-spaced pulses | Irregular gaps or missing pulse cycles detected |
| Wheel speed sensor signal amplitude | Stable AC signal within 0.5–5V range | Erratic or dropout signal indicating tone ring defect |
Code C1143 is classified as a serious fault. If your check engine light is flashing — not just steady — pull over safely and do not continue driving. A flashing CEL indicates an active misfire or critical failure that can cause catalytic converter damage within minutes or permanent engine harm within miles. Contact a certified mechanic immediately. Do not attempt roadside repairs on high-severity codes unless you are trained to do so.
Once the fault is repaired, C1143 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.