C0243

Code

Generic C — Chassis

ABS/ESC Wheel Speed Sensor Circuit Malfunction

Brand: Generic

Type: C — Chassis

Views: UK: 19 EN: 17 RU: 14

AI status

Completed

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Page language: EN

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