C0050 – Rear Wheel Speed Sensor Circuit

C0050 – Rear Wheel Speed Sensor Circuit indicates that the ABS/ESC module has detected an electrical fault, unstable signal, or loss of signal from one of the rear wheel speed sensors. These sensors provide critical wheel-speed information used by ABS, traction control, stability control, AWD systems, and cruise control. When a rear sensor malfunctions, the vehicle may lose traction control, experience unexpected ABS activation, or show warning lights. This guide explains what C0050 means, symptoms, causes, how to diagnose it, and the most effective repairs.

What Does C0050 Mean?

C0050 is a generic chassis code set when the ABS module identifies a problem in the rear wheel speed sensor circuit. The signal may be weak, inconsistent, or missing. Depending on the vehicle, the code may refer to either rear sensor or specifically “right rear” or “left rear.” The ABS module expects smooth, consistent pulses from the tone ring or magnetic encoder; any interruption prompts the code.

Rear wheel sensors are exposed to harsh conditions—road debris, mud, salt, and water—which commonly leads to wiring corrosion, damaged connectors, or tone ring failure. In some models, the sensor is integrated into the hub assembly, requiring hub replacement if it fails.

Quick Reference

  • OBD-II Family: C-Code (Chassis)
  • Scope: Generic
  • System: ABS / Traction / Stability Control
  • Difficulty Level: Easy–Moderate
  • Estimated Repair Cost: €70–€300+
  • Last Updated: 22 November 2025

Real-World Example / Field Notes

A compact SUV arrived with ABS and traction-control lights on. The live data stream showed the right rear sensor reading 0 km/h while the other wheels showed accurate speeds. Inspection revealed that the harness had rubbed against the rear control arm, cutting through the insulation. Repairing the wiring resolved the issue instantly.

In another case, a sedan experienced unwanted ABS activation at low speeds. The rear tone ring on the axle had cracked due to rust expansion, creating irregular pulse spacing. Replacing the tone ring restored smooth braking performance and cleared C0050.

Symptoms of C0050 – Rear Wheel Speed Sensor Circuit

  • ABS warning light: ABS disabled due to missing rear wheel speed data.
  • Traction or ESC lights: Stability systems unable to calculate wheel slip.
  • Unexpected ABS activation: Especially during low-speed braking.
  • Cruise control disabled: Requires accurate wheel-speed signals.
  • Harsh or delayed shifting: Transmission logic may rely on rear wheel speed.
  • Speedometer fluctuations (rare): Some vehicles use rear wheel speed as reference.
  • AWD performance issues: Torque distribution may become unstable.

Common Causes of C0050

Most Common Causes

  • Failed rear wheel speed sensor
  • Damaged sensor wiring due to rubbing, corrosion, or road debris
  • Cracked or rusted reluctor/tone ring
  • Debris or metallic particles stuck to the sensor tip
  • Incorrect sensor gap caused by rust buildup or improper installation

Less Common Causes

  • Failed rear hub assembly with integrated sensor
  • Water intrusion at ABS module or sensor connector
  • Incorrect tire size causing speed discrepancies
  • Damaged CAN wiring affecting speed-signal broadcast
  • Internal ABS/ESC module malfunction

Diagnosis: Step-by-Step Guide

Diagnosing C0050 requires checking rear wheel-speed data, inspecting wiring, and confirming sensor performance.

Tools You’ll Need

Advanced OBD-II scanner, multimeter, wiring diagrams, jack/stands, backprobe leads, cleaning tools, and an optional oscilloscope.

  1. Scan all modules: Look for additional ABS or wheel-speed sensor codes.
  2. Check live wheel-speed data: Drive slowly and compare rear sensor outputs to the front wheels.
  3. Inspect rear sensor wiring: Look for cuts, corrosion, or rubbing damage near suspension components.
  4. Remove rear sensor (if possible): Check for rust buildup or debris stuck to the magnetic tip.
  5. Inspect tone ring or encoder: Look for cracks, rust swelling, missing teeth, or wobble.
  6. Measure sensor resistance: Compare to manufacturer specifications.
  7. Backprobe sensor output: Check for clean AC or digital pulses while spinning the wheel.
  8. Check hub assembly: If the sensor is integrated, inspect bearing condition and play.
  9. Inspect ABS module connectors: Check for moisture or corrosion.
  10. Oscilloscope test: Identify signal dropouts or distorted patterns.

Pro Tip: Rust expansion around the sensor mounting surface can push the sensor too far from the tone ring, creating weak or intermittent signals. Cleaning the mounting area often resolves C0050 without replacing parts.

Possible Fixes & Repair Costs

  • Replace rear wheel speed sensor: €70–€150
  • Repair or replace sensor wiring: €60–€180
  • Replace tone ring/reluctor wheel: €80–€200
  • Replace rear hub/bearing assembly: €120–€300+
  • Clean sensor and mounting area: €0–€50
  • ABS module repair/replacement: €350–€650+

Can I Still Drive With C0050?

You can usually drive, but ABS, traction control, and ESC may be disabled. This increases stopping distances and reduces stability on wet or slippery roads. If the vehicle experiences harsh shifting or unexpected ABS activation, it’s best to avoid driving until repairs are made.

Related Codes

  • C0055 – Wheel Speed Sensor Circuit
  • C0051 – Right Rear Wheel Speed Sensor Circuit Range/Performance
  • C0045 – Left Rear Wheel Speed Sensor Circuit
  • C0041 – Right Front Wheel Speed Sensor Circuit Range/Performance
  • C0040 – Right Front Wheel Speed Sensor Circuit
  • C0035 – Left Front Wheel Speed Sensor Circuit
  • C0000 – Vehicle Speed Information Circuit Malfunction

Key Takeaways

  • C0050 indicates a malfunction in the rear wheel speed sensor circuit.
  • Common causes include wiring damage, bad sensors, and cracked tone rings.
  • ABS, traction control, cruise control, and AWD systems may be affected.
  • Diagnosis is straightforward using live-data comparison and visual inspection.

FAQ

Does C0050 always mean the sensor is bad?

No. Wiring damage or a cracked tone ring can trigger the code even with a good sensor.

Will C0050 disable traction control?

Yes. Stability systems require accurate rear-wheel speed data.

Can mismatched rear tires cause C0050?

Rarely, but large differences in circumference can confuse ABS logic.

Is it safe to drive with C0050?

Driving is possible, but reduced ABS and traction control increase stopping distance and instability.

Do I need to replace the ABS module?

Only if all sensors, wiring, and tone rings check out and the module is confirmed faulty.