Code
C0243
Generic
C — Chassis
ABS/ESC Wheel Speed Sensor Circuit Malfunction
Views:
UK: 9
EN: 8
RU: 5
AI status
Completed
Completed
100%
Causes
- Damaged or intermittent wheel speed sensor (tone wheel sensor / pickup)
- Broken, chafed or corroded wiring or connector (open, short to ground or short to battery)
- Contaminated or damaged tone ring (missing teeth, heavy rust or debris)
- Poor sensor air gap (too large) or sensor misalignment
- Faulty ABS/ESC control module or internal driver circuit
- Poor ground or supply voltage to the ABS sensor circuit
Symptoms
- ABS warning lamp and ESC/traction control warning lamp illuminated
- ABS or ESC intervention may be disabled; traction control may be reduced or unavailable
- Possible pulsating brake pedal under ABS activation or altered brake feel
- Traction control or stability faults during cornering or low-traction conditions
- Vehicle speed display or cruise control acting erratically on some vehicles (if speed sensor shared)
What to check
- Read freeze frame/fault details and any additional ABS/ECU codes to identify affected wheel/circuit
- Visually inspect the wheel speed sensor, tone ring/reluctor and wiring harness at the affected corner
- Check sensor connector for corrosion, bent pins, moisture ingress and secure fit
- Measure sensor resistance (for passive sensors) and compare to specification; check reference voltage for active sensors
- Perform continuity and insulation tests on wiring back to ABS module (look for short to ground/12V and open circuits)
- Inspect wheel bearing and hub for play or damage that could affect sensor gap
Signal parameters
- Passive (variable reluctance) sensor: DC resistance typically ~500–2000 Ω (manufacturer specific); produces AC sine/alternating voltage whose amplitude rises with wheel speed (may reach several volts peak-to-peak at road speeds)
- Active (Hall/active) sensor: requires reference voltage (commonly 5 V or battery dependent) and produces a digital/pulse (square) output (0–5 V or 0–12 V depending on system) with frequency proportional to wheel speed
- Expected waveform: clean, regular pulses corresponding to tone ring teeth; frequency increases with wheel speed; missing or irregular pulses indicate tone ring or sensor issue
- Typical air-gap tolerance: roughly 0.5–3.0 mm (vehicle-specific); larger gaps reduce amplitude or drop pulses
Diagnostic algorithm
- Retrieve ABS/ESC fault data and note affected wheel/circuit, freeze frame, and occurrence conditions.
- Visually inspect the sensor, tone ring and wiring at the reported wheel for damage, debris, corrosion or oil contamination.
- With connector disconnected, measure passive sensor DC resistance (if applicable) and compare to spec; for active sensors, verify reference supply and ground present at connector with ignition ON.
- Back-probe the sensor connector with a scope or multimeter and spin the wheel by hand (or use a scan tool wheel speed display) to confirm expected pulse waveform/frequency and amplitude.
- Wiggle the harness and move suspension through travel while monitoring signal to find intermittent opens or shorts.
- Perform continuity/insulation testing of the wiring from the sensor connector back to the ABS module; check for short to ground or battery and for opens.
- Inspect tone ring for missing/damaged teeth, heavy rust or debris; repair or replace if damaged. Check wheel bearing for excessive play and replace if it alters sensor gap/reference.
- If wiring and sensor check OK, verify ABS module power/grounds and attempt to clear codes; if fault returns and all wiring/sensor tests pass, consider module output driver fault and follow manufacturer module diagnostic/repair procedures.
- After repair or replacement, clear codes and perform road test or test drive to confirm fault does not recur and ABS/ESC systems operate normally.
Likely causes
- Connector corrosion or loose connector at hub (very common)
- Damaged sensor from road debris or improper servicing
- Wire chafe near wheel or inside suspension travel area
- Tone ring damage from impact or corrosion causing intermittent pulses
Fault status
Status
ABS/ESC: Wheel speed sensor circuit malfunction detected. ABS/ESC warning light illuminated; one wheel speed sensor circuit is reporting abnormal or no signal. Stability control/traction may be unavailable until fault is corrected.
Repair difficulty: Medium
Diagnostic time: 1-2 hours
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