ABS Wheel Speed Sensor Tone Ring Fault
The C1139 code indicates that the ABS control module has detected an anomaly in a wheel speed sensor signal caused by a missing tooth on the associated tone ring (reluctor). The tone ring, typically integrated into the wheel hub, bearing, or axle shaft, modulates the sensor's magnetic field to generate a frequency signal proportional to wheel speed. A missing tooth disrupts the expected pulse pattern, preventing the module from accurately calculating wheel speed. As a result, the system may disable ABS, traction control (TCS), and electronic stability control (ESC) to prevent erroneous interventions.
1. Commonly Affected Makes
2. Most Common Causes
- Damaged, cracked, or broken/missing teeth on the tone ring due to impact or fatigue
- Defective wheel bearing with an integrated tone ring
- Rust, dirt, or metal debris buildup on the tone ring affecting sensor reading
- Wheel speed sensor misaligned or with incorrect air gap relative to the tone ring
- Replaced CV axle with incorrect tone ring, damaged during installation, or missing reference tooth
- Corroded or poor contact at wheel speed sensor connectors
3. Symptoms You Will Notice
- ABS warning light illuminated on dashboard
- Traction control and stability control warning lights may also be on
- ABS, TCS, and ESC systems may be disabled or inoperative
4. Step-by-Step Diagnosis
Scan for codes and verify C1139 is present
Inspect the tone ring for damage, missing teeth, rust, or debris
Check wheel bearing condition if tone ring is integrated
Measure sensor air gap and alignment; adjust if necessary
Test sensor connector for corrosion or poor contact
If CV axle was replaced, verify correct tone ring and proper installation
5. Frequently Asked Questions
Is it safe to drive?▼
Driving is possible but not recommended because ABS, traction control, and stability control may be disabled, increasing the risk of skidding or loss of control in emergency maneuvers or slippery conditions.
How much does it cost to fix?▼
Repair costs typically range from $200 to $800 USD, depending on whether the tone ring is replaceable separately or requires replacing the wheel bearing or CV axle.