Code
C0252
Generic
C — Chassis
ABS Wheel Speed Sensor Circuit Fault (Sensor 2)
Views:
UK: 7
EN: 6
RU: 5
AI status
Completed
Completed
100%
Causes
- Faulty wheel speed sensor (Sensor 2)
- Open or shorted wiring between sensor and ABS module
- Corroded, loose or contaminated connector
- Damaged or missing tone/ring reluctor on the wheel/hub
- Damaged wheel bearing or excessive air gap altering the signal
- Faulty ABS control module or poor ground/shielding
Symptoms
- ABS warning lamp ON (may also show traction/ESC lamp)
- ABS or traction control disabled (reduced braking performance under ABS events)
- Intermittent ABS/traction warnings when cornering or over bumps
- Possible inconsistent wheel speed reading in live data
- Occasional ABS activation when not required (rare)
What to check
- Retrieve and record freeze-frame and live-data for all ABS wheel speed sensors
- Identify which wheel is Sensor 2 for the specific vehicle application
- Visual inspection of sensor, connector and wiring for damage, corrosion or foreign material
- Compare live wheel speed readings for Sensor 2 vs opposite wheel while rotating wheel
- Check for presence of tone/reluctor and inspect for damage or missing teeth
- Measure sensor resistance and continuity to the ABS module connector
Signal parameters
- Sensor types: passive (variable reluctance/VR) or active (Hall/active magnetic) — verify vehicle type
- Passive VR typical DC resistance (generic): ~800–2,000 ohms (varies by design) — open/infinite indicates break
- Passive VR output: AC voltage that increases with wheel speed; low speeds produce tens to hundreds of mV, higher speeds produce volts
- Active sensor: 5 V reference supply; output is a square/pulse ~0–5 V (or 0–12 V on some systems) proportional to speed
- Typical static: 0 V output at rest (active) or 0 mV (passive); waveform frequency increases with wheel rotation speed
- Continuity: short to ground or to power will show low ohms; open shows very high/infinite
Diagnostic algorithm
- Read and record current ABS codes and freeze-frame data. Note vehicle speed and conditions when fault set.
- Confirm which wheel is Sensor 2 from manufacturer documentation or wiring diagrams.
- Visually inspect the sensor, connector and harness for damage, corrosion, loose clips, rubbing or crushed wiring.
- Backprobe connector with ignition ON: check for correct reference voltage (if active sensor) and good ground.
- Measure sensor DC resistance (for passive sensor) and compare to specification; open or short indicates faulty sensor.
- With wheel lifted and safe supports in place, spin the wheel and observe live data for Sensor 2 vs the opposite wheel using a scan tool.
- Use a multimeter set to AC mV (for VR) or a scope (recommended) to observe waveform while wheel is rotated; look for clean waveform without dropouts or noise.
- Wiggle harness and connectors while monitoring live data to reveal intermittent faults. Inspect tone ring for missing or damaged teeth and clean if contaminated.
- If wiring fault suspected, perform continuity and short-to-power/ground tests between sensor connector and ABS module connector; repair any damaged wiring or connector pins.
- Replace sensor or tone ring if found defective. If wiring and sensor are good but no signal at ABS module input, consider module fault and confirm power/ground to module before replacement.
- Clear codes and perform a test drive to verify the fault does not return and that ABS/traction function is restored.
Likely causes
- Sensor damaged by road debris or corrosion
- Connector pin corrosion or poor connection at sensor
- Broken or chafed harness near wheel or suspension
- Reluctor (tone) ring cracked, missing teeth or contaminated
Fault status
Status
C0252 — ABS Wheel Speed Sensor Circuit Fault (Sensor 2). The ABS control module has detected an implausible, missing, open or shorted wheel speed sensor signal for Sensor 2. ABS/traction control may be limited or disabled.
Repair difficulty: Medium
Diagnostic time: 1.5-3.0 hours
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