C0145

Code

Generic C — Chassis

ABS Wheel Speed Sensor Circuit Fault

Brand: Generic

Type: C — Chassis

Views: UK: 13 EN: 20 RU: 13

AI status

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Page language: EN

Causes

Damaged or failed wheel speed (ABS) sensor
Open, shorted or corroded wiring or connector
Damaged or missing tone ring (reluctor) or magnet ring
Contaminated sensor face (metal debris, grease, brake dust)
Poor ground or power supply to the sensor circuit
Faulty ABS control module or internal driver failure

Symptoms

ABS warning lamp illuminated
Traction control / ESC light may also be on
Possible loss of ABS functionality during braking
ABS/traction intervention may be disabled or erratic
Occasional or constant fault present in vehicle diagnostic scanner
Noise or unusual play at hub/wheel (if bearing or tone ring damaged)

What to check

Read stored and pending ABS codes with a capable scan tool; note which wheel is affected
Compare live wheel speed sensor readings while vehicle is rolling — look for a sensor that reads 0 or is significantly different
Visually inspect sensor, connector and wiring for damage, corrosion, pin push-out or contamination
Check connector seals and mating surfaces; backprobe voltage and ground with ignition on
Measure sensor resistance (if applicable) and compare to manufacturer spec
Inspect tone/reluctor ring for missing teeth, heavy rust, debris or contact with sensor

Signal parameters

Hall-effect sensor: digital square wave referenced to 0–5 V (or 0–12 V on some systems); frequency proportional to wheel speed
Variable reluctance (VR) sensor: AC sinusoidal/pulsed voltage whose amplitude increases with wheel speed (may be a few hundred millivolts to several volts)
At rest: near 0 V DC; when wheel spins: discrete pulses at frequency = wheel speed × number of tone teeth
Expected behaviour: consistent, regular pulses with amplitude and frequency proportional to wheel rotation; no constant DC short to battery or ground
If resistance measured: open circuit (infinite) or very low shorted value indicates sensor or wiring fault (refer to vehicle spec for exact ohms)

Diagnostic algorithm

Connect a scan tool and read ABS codes and live wheel speed data to identify which wheel circuit is flagged.
Visually inspect the flagged wheel sensor, tone ring and harness for damage, contamination, loose fasteners or rubbing.
With ignition ON (engine off), backprobe the sensor connector: verify reference power (if applicable), ground, and sensor output behavior while spinning the wheel by hand or lift.
Measure sensor resistance (for VR sensors) and compare to spec. If hall sensor, check reference voltage and switching to ground.
Use a lab scope or multimeter to inspect waveform while spinning the wheel. Look for missing pulses, low amplitude, excessive noise or flat lines.
Perform a wiggle test on the wiring from sensor to ABS module while monitoring live data to find intermittent opens/shorts.
Inspect tone/reluctor ring for damaged, bent or missing teeth and check hub/bearing axial/radial play that could alter the gap.
Check continuity and insulation between sensor wiring and chassis ground/power for shorts. Repair wiring or connector as needed.
If sensor and wiring check good, verify ABS module pin voltages and grounds. Swap sensors (if practical and documented) to see if fault follows sensor.
After repair or replacement, clear codes and road test to confirm proper operation and that wheel speed readings are consistent across all wheels.

Likely causes

Corroded/loose connector or broken wiring at the sensor
Failed wheel speed sensor
Damaged or heavily contaminated tone/reluctor ring
Intermittent short to ground or battery voltage in sensor circuit
ABS module input or ground fault (less common)

Fault status

⚠️ Status

ABS control module reports a fault in a wheel speed sensor circuit — signal missing, intermittent, shorted or out of expected range. Further testing required to identify whether sensor, wiring, tone ring or module is at fault.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours