Code
C0122
Generic
C — Chassis
Wheel Speed Sensor Circuit Fault — Rear Right
Views:
UK: 3
EN: 4
RU: 4
AI status
Completed
Completed
100%
Causes
- Damaged or failed rear-right wheel speed sensor
- Broken, pinched, corroded or disconnected wiring/connector at the sensor
- Axle/tone ring (reluctor) missing, chipped or contaminated
- Poor ground or reference supply to the sensor
- Intermittent connection due to corrosion or damaged pin
- Faulty ABS/traction control module or internal driver fault
Symptoms
- ABS warning light illuminated
- Traction/stability control warning light illuminated or disabled
- Loss or limited operation of ABS and traction control functions
- Possible erratic ABS activation or reduced braking stability
- Noisy or missing wheel speed reading for rear-right on scan tool
- Occasional speedometer/cluster anomalies (depending on vehicle)
What to check
- Read stored/freeze-frame DTCs and note any related codes
- Visually inspect rear-right wheel sensor, connector, and wiring for damage or corrosion
- Check tone ring/reluctor for missing teeth, cracks, heavy rust or debris
- Use a scan tool to view live wheel speed sensor data while rotating wheel
- Wiggle harness and connector while monitoring live data for intermittent faults
- Measure sensor resistance and compare to manufacturer spec
Signal parameters
- Passive (magnetic) sensor: AC voltage that rises with wheel speed (mV to several hundred mV depending on speed)
- Active (hall/VR with electronics) sensor: pulsed/square wave or 0–5 V digital signal; frequency increases with wheel speed
- Reference supply for active sensors typically ~5 V; ground should be stable
- Intermittent or zero signal while wheel spins indicates open, short or sensor failure
- Short to ground or battery may show constant low/high voltage rather than a pulsed signal
Diagnostic algorithm
- Verify code and any related DTCs with a scan tool; record freeze-frame/live data.
- Perform a visual inspection of the rear-right sensor, connector and wiring for damage, corrosion, or pin push-out; repair as needed.
- Inspect the tone ring/reluctor on the hub or axle for missing teeth, heavy corrosion, or debris; clean or replace if damaged.
- With ignition on, check for proper reference voltage and ground at the sensor connector (active sensor).
- Measure sensor resistance (if passive) or back-probe the signal circuit while spinning the wheel; use an oscilloscope for best results to verify waveform.
- Wiggle the harness and connector while monitoring live data to find intermittent faults; repair broken wires and secure harness routing away from pinch points.
- If wiring and sensor test good but fault persists, check continuity from sensor connector to ABS module connector and inspect module grounds.
- Replace the wheel speed sensor if it fails output or resistance tests, then clear codes and perform a road test to confirm repair.
- If code remains after sensor/wiring replacement and tests, consider ABS module diagnosis or replacement per manufacturer procedures.
Likely causes
- Wiring/connector damage or corrosion at rear-right sensor
- Failed rear-right wheel speed sensor
- Damaged or missing tone ring/reluctor on rear-right hub
- Poor sensor reference/ground
- Intermittent harness damage near suspension or axle
Fault status
Status
Rear right wheel speed sensor circuit fault detected. ABS/traction control may be disabled or operating with limited functionality until the fault is corrected.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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