Code
C0221
Generic
C — Chassis
Wheel Speed Sensor Circuit Malfunction
Views:
UK: 0
EN: 0
RU: 0
AI status
Completed
Completed
100%
Causes
- Broken or damaged sensor wiring/harness (chafing, corrosion, broken wires)
- Connector corrosion, loose terminal, or poor mating
- Failed wheel speed sensor (passive or active)
- Damaged or missing tone/reluctor ring (chipped, missing teeth, heavy rust or debris)
- Wheel bearing damage causing sensor displacement
- Faulty ABS/traction control module or poor module ground/power
Symptoms
- ABS, traction control or stability warning light illuminated
- One wheel shows different or no speed reading on a scan tool/live data
- Pulsating brake pedal during normal braking (when ABS engages)
- Loss of ABS/traction control functions, longer stopping distances in emergency braking
- Inconsistent speedometer reading (on some vehicles)
- Diagnostic Trouble Codes stored for specific wheel sensors and/or ABS module communication faults
What to check
- Retrieve freeze-frame data and full ABS/traction codes with a capable scan tool
- Compare live wheel speed sensor values at low speed — all four should change smoothly and similarly
- Visually inspect sensor, connector and wiring at the affected wheel(s) for damage, corrosion, or disconnection
- Inspect tone/reluctor ring for missing/damaged teeth, heavy rust, debris, or excessive runout
- Wiggle harness while watching live data to find intermittent faults
- Check ABS module power and ground circuits and connector condition
Signal parameters
- Passive (variable-reluctance) sensor: measurable AC voltage that increases with wheel speed; expect low millivolts to volts depending on speed (amplitude and frequency rise with rpm). Typical resistance range varies by maker (often several hundred to a few thousand ohms) — consult vehicle spec.
- Active (Hall/VR active) sensor: supply/reference typically 5 V or 12 V; output is a digital/pulsed waveform that toggles between ~0–5 V (or 0.5–4.5 V) with frequency proportional to wheel speed.
- When stationary: sensor output should be a steady baseline (no random pulses).
- Short to ground or open circuits typically show no signal or stuck/erratic values in live data.
Diagnostic algorithm
- Safety first: park on level ground, chock wheels, and support vehicle with jack stands before working at a wheel.
- Confirm code and note freeze-frame, occurrence count and whether code is specific to a wheel (e.g., left front).
- Scan live data: observe wheel speed sensor readings while slowly rolling vehicle (or driving at low speed) and rotate suspect wheel by hand with connector connected. Look for zero, intermittent, or noisy signals.
- Visually inspect sensor, tone ring, and wiring/connector for physical damage, contamination, missing teeth, or excessive gap.
- Unplug connector and inspect terminals for corrosion, bent pins or water ingress. Clean and repair as needed.
- Check sensor wiring continuity and for shorts: measure resistance between sensor and module connector; check for short to ground or battery. Wiggle harness while monitoring to replicate intermittent faults.
- For passive sensors: measure coil resistance and AC output while rotating wheel (use an oscilloscope if available) — compare to spec. For active sensors: verify reference voltage to sensor and observe switching output with a scope or DVM (frequency/pulses while wheel spins).
- If sensor and wiring test good but signal still absent or erratic, inspect tone ring runout and gap; repair or replace damaged tone ring or wheel bearing if out of spec.
- If wiring and mechanical parts are good, check ABS module connector, power/ground and CAN/communication lines. Consider module fault if all others check good.
- After repair, clear codes, re-test (road test) and verify no reoccurrence. Monitor live data to confirm proper signals from all wheels.
Likely causes
- Corroded/loose connector at the sensor
- Damaged wiring harness at wheel (common at suspension joints)
- Sensor failure (most common on high-mileage vehicles)
- Damaged or contaminated tone/reluctor ring
Fault status
Status
Wheel speed sensor circuit malfunction detected. Possible open/short, poor connection, faulty sensor, or damaged tone ring. ABS/traction control functionality may be reduced or disabled until repaired.
Repair difficulty: Medium
Diagnostic time: 0.5–2.0 hours
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Code
C0221
HUMMER
C — Chassis
Right Rear Wheel Speed Sensor Circuit Fault
Views:
UK: 17
EN: 23
RU: 17
AI status
Completed
Completed
100%
Causes
- Broken or damaged sensor wiring/harness (chafing, corrosion, broken wires)
- Connector corrosion, loose terminal, or poor mating
- Failed wheel speed sensor (passive or active)
- Damaged or missing tone/reluctor ring (chipped, missing teeth, heavy rust or debris)
- Wheel bearing damage causing sensor displacement
- Faulty ABS/traction control module or poor module ground/power
Symptoms
- ABS, traction control or stability warning light illuminated
- One wheel shows different or no speed reading on a scan tool/live data
- Pulsating brake pedal during normal braking (when ABS engages)
- Loss of ABS/traction control functions, longer stopping distances in emergency braking
- Inconsistent speedometer reading (on some vehicles)
- Diagnostic Trouble Codes stored for specific wheel sensors and/or ABS module communication faults
What to check
- Retrieve freeze-frame data and full ABS/traction codes with a capable scan tool
- Compare live wheel speed sensor values at low speed — all four should change smoothly and similarly
- Visually inspect sensor, connector and wiring at the affected wheel(s) for damage, corrosion, or disconnection
- Inspect tone/reluctor ring for missing/damaged teeth, heavy rust, debris, or excessive runout
- Wiggle harness while watching live data to find intermittent faults
- Check ABS module power and ground circuits and connector condition
Signal parameters
- Passive (variable-reluctance) sensor: measurable AC voltage that increases with wheel speed; expect low millivolts to volts depending on speed (amplitude and frequency rise with rpm). Typical resistance range varies by maker (often several hundred to a few thousand ohms) — consult vehicle spec.
- Active (Hall/VR active) sensor: supply/reference typically 5 V or 12 V; output is a digital/pulsed waveform that toggles between ~0–5 V (or 0.5–4.5 V) with frequency proportional to wheel speed.
- When stationary: sensor output should be a steady baseline (no random pulses).
- Short to ground or open circuits typically show no signal or stuck/erratic values in live data.
Diagnostic algorithm
- Safety first: park on level ground, chock wheels, and support vehicle with jack stands before working at a wheel.
- Confirm code and note freeze-frame, occurrence count and whether code is specific to a wheel (e.g., left front).
- Scan live data: observe wheel speed sensor readings while slowly rolling vehicle (or driving at low speed) and rotate suspect wheel by hand with connector connected. Look for zero, intermittent, or noisy signals.
- Visually inspect sensor, tone ring, and wiring/connector for physical damage, contamination, missing teeth, or excessive gap.
- Unplug connector and inspect terminals for corrosion, bent pins or water ingress. Clean and repair as needed.
- Check sensor wiring continuity and for shorts: measure resistance between sensor and module connector; check for short to ground or battery. Wiggle harness while monitoring to replicate intermittent faults.
- For passive sensors: measure coil resistance and AC output while rotating wheel (use an oscilloscope if available) — compare to spec. For active sensors: verify reference voltage to sensor and observe switching output with a scope or DVM (frequency/pulses while wheel spins).
- If sensor and wiring test good but signal still absent or erratic, inspect tone ring runout and gap; repair or replace damaged tone ring or wheel bearing if out of spec.
- If wiring and mechanical parts are good, check ABS module connector, power/ground and CAN/communication lines. Consider module fault if all others check good.
- After repair, clear codes, re-test (road test) and verify no reoccurrence. Monitor live data to confirm proper signals from all wheels.
Likely causes
- Corroded/loose connector at the sensor
- Damaged wiring harness at wheel (common at suspension joints)
- Sensor failure (most common on high-mileage vehicles)
- Damaged or contaminated tone/reluctor ring
Fault status
Status
Wheel speed sensor circuit malfunction detected. Possible open/short, poor connection, faulty sensor, or damaged tone ring. ABS/traction control functionality may be reduced or disabled until repaired.
Repair difficulty: Medium
Diagnostic time: 0.5–2.0 hours
Similar codes
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