Left Front Wheel Speed Sensor Circuit Malfunction
Diagnostic trouble code C1155 indicates a fault in the left front wheel speed sensor circuit. This sensor, also known as an ABS or WSS sensor, generates a pulse signal that the ABS control module uses to monitor wheel rotation speed. The code sets when the module detects a missing, erratic, or out-of-range signal from the left front sensor circuit, preventing proper operation of the ABS, traction control, or stability control systems.
1. Commonly Affected Makes
2. Most Common Causes
- Damaged or worn left front wheel speed sensor
- Corroded, loose, or disconnected sensor connector
- Open, shorted, or high-resistance wiring in the sensor harness
- Damaged, dirty, or misaligned tone ring (reluctor ring)
- Faulty ABS control module
- Excessive air gap between the sensor and tone ring
3. Symptoms You Will Notice
- ABS warning light illuminated on the dashboard
- Traction control or stability control warning lights may also be on
- ABS system may not function, potentially causing wheel lockup during hard braking
- Loss of traction control or stability assist
4. Step-by-Step Diagnosis
Scan the ABS module for codes and record freeze frame data
Visually inspect the left front wheel speed sensor connector and wiring for damage, corrosion, or loose connections
Measure sensor resistance and compare to specifications (typically 1-2 kΩ)
Check for AC voltage output from the sensor while spinning the wheel (should produce a clean sine wave)
Inspect the tone ring for damage, debris, or runout
If all else is normal, test the ABS module by substitution or further diagnostics
5. Frequently Asked Questions
Is it safe to drive?▼
Driving with code C1155 is not recommended because the ABS, traction control, and stability control systems may be disabled. In emergency braking, wheels could lock up, increasing stopping distance and risk of loss of control. Have the vehicle diagnosed and repaired as soon as possible.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400. A new wheel speed sensor costs $30–$100, and labor is about $100–$200. If wiring or the tone ring needs repair, costs may be higher.