C0225 — ABS Left Rear Wheel Speed Sensor Circuit Malfunction

Causes

• Open or shorted wiring between left rear wheel speed sensor and ABS module
• Corroded, loose, or damaged sensor connector or pins
• Failed wheel speed sensor (passive or active type)
• Damaged or missing tone ring (reluctor) or excessive air gap
• Wheel bearing or hub damage causing incorrect sensor-air gap or noise
• Poor ground or supply/reference voltage problem

Symptoms

• ABS warning light and/or traction control (TC/ESP) light illuminated
• Possible reduced or disabled ABS/traction control operation
• Inconsistent wheel speed reading for left rear on scan tool or dash
• ABS activation or unexpected braking behavior during conditions that would normally trigger ABS
• Occasional intermittent fault that may clear and return
• Noise from rear hub or rough wheel bearing feel (if mechanical damage present)

What to check

• Read and record freeze frame and complete ABS code history with a diagnostic scanner
• Visually inspect left rear sensor, tone ring/reluctor, connector, and wiring for damage, corrosion, or contamination
• Check connector pins for corrosion, bent pins, or water entry and ensure secure fit
• Backprobe the sensor connector with ignition on (or powered as required) to verify reference, ground, and signal where applicable
• Measure sensor resistance (for passive sensors) and compare to specification or expected range
• Use an oscilloscope or fast-data tool to view wheel speed signal while rotating the wheel to verify waveform and amplitude

Signal parameters

• Passive (inductive) sensor: produces AC voltage that increases with wheel speed; amplitude typically small at low speed (tens to hundreds of millivolts) and rises with RPM (can reach volts at higher speeds) — resistance of a passive sensor typically in the hundreds to low thousands of ohms (varies by design)
• Active (Hall or magnetoresistive) sensor: typically has a 5 V (or vehicle-specific) reference supply and ground; signal is a digital/pulsed waveform switching between ~0 V and reference voltage with frequency proportional to wheel speed
• Waveform: clean periodic sine-like (passive) or square wave (active); missing pulses, clipped amplitude, excessive noise, or irregular spacing indicate problems
• Frequency: increases with wheel speed (low Hz at slow speed to tens/hundreds of Hz at higher speed); compare left rear to other wheels for consistency

Similar codes

Causes

• Open or shorted wiring between left rear wheel speed sensor and ABS module
• Corroded, loose, or damaged sensor connector or pins
• Failed wheel speed sensor (passive or active type)
• Damaged or missing tone ring (reluctor) or excessive air gap
• Wheel bearing or hub damage causing incorrect sensor-air gap or noise
• Poor ground or supply/reference voltage problem

Symptoms

• ABS warning light and/or traction control (TC/ESP) light illuminated
• Possible reduced or disabled ABS/traction control operation
• Inconsistent wheel speed reading for left rear on scan tool or dash
• ABS activation or unexpected braking behavior during conditions that would normally trigger ABS
• Occasional intermittent fault that may clear and return
• Noise from rear hub or rough wheel bearing feel (if mechanical damage present)

What to check

• Read and record freeze frame and complete ABS code history with a diagnostic scanner
• Visually inspect left rear sensor, tone ring/reluctor, connector, and wiring for damage, corrosion, or contamination
• Check connector pins for corrosion, bent pins, or water entry and ensure secure fit
• Backprobe the sensor connector with ignition on (or powered as required) to verify reference, ground, and signal where applicable
• Measure sensor resistance (for passive sensors) and compare to specification or expected range
• Use an oscilloscope or fast-data tool to view wheel speed signal while rotating the wheel to verify waveform and amplitude

Signal parameters

• Passive (inductive) sensor: produces AC voltage that increases with wheel speed; amplitude typically small at low speed (tens to hundreds of millivolts) and rises with RPM (can reach volts at higher speeds) — resistance of a passive sensor typically in the hundreds to low thousands of ohms (varies by design)
• Active (Hall or magnetoresistive) sensor: typically has a 5 V (or vehicle-specific) reference supply and ground; signal is a digital/pulsed waveform switching between ~0 V and reference voltage with frequency proportional to wheel speed
• Waveform: clean periodic sine-like (passive) or square wave (active); missing pulses, clipped amplitude, excessive noise, or irregular spacing indicate problems
• Frequency: increases with wheel speed (low Hz at slow speed to tens/hundreds of Hz at higher speed); compare left rear to other wheels for consistency

Similar codes