Code
C2421
Generic
C — Chassis
ABS Wheel Speed Sensor Circuit – Front Left Intermittent
Views:
UK: 2
EN: 1
RU: 2
AI status
Completed
Completed
100%
Causes
- Damaged or chafed wiring in the front-left wheel speed sensor circuit
- Corroded, loose, or contaminated connector or pin at the sensor or ABS module
- Failed or intermittent wheel speed sensor (Hall-effect or variable-reluctance)
- Excessive air gap, misalignment, contamination (metal shavings, dirt) between sensor and tone/reluctor ring
- Damaged, missing or heavily corroded tone/reluctor wheel teeth
- Poor ground or power supply fault to the active sensor
Symptoms
- ABS warning lamp illuminated (may be intermittent)
- Traction/stability control warning or loss of traction control functionality
- Intermittent operation of ABS/ESC systems under braking or slippery conditions
- Inconsistent or dropping wheel speed reading for front-left when monitoring live data
- Possible pulsating brakes or reduced ABS performance during an event
What to check
- Read ABS codes and any freeze-frame/fault timestamps with a scan tool
- Monitor live wheel speed sensor values for all four corners while turning the wheels by hand and during a low-speed road test
- Visually inspect front-left sensor, wiring harness, and connector for damage, corrosion, pin damage, or contamination
- Perform a wiggle test on the wiring and connector while watching live data or using an oscilloscope to reproduce the intermittent behavior
- Back-probe connector to verify supply voltage (if active sensor) and ground integrity
- Measure sensor resistance (for passive sensors) and check AC output while spinning the wheel
Signal parameters
- Active (Hall/active) sensor: typically has a reference supply (usually ~5 V) and outputs a digital/square-wave or open-collector pulse—signal toggles between near 0 V and supply voltage as the wheel turns
- Passive (variable-reluctance) sensor: no supply; produces AC voltage proportional to wheel speed (measurable AC voltage when wheel is rotated). Low-speed AC may be ~0.1–1 Vrms and increases with speed (exact values are manufacturer-specific)
- Typical diagnostic checks: sensor resistance (passive sensor) — manufacturer spec varies; compare to opposite side and service manual values
- Signal waveform: regular pulses at consistent frequency as wheel rotates; amplitude and shape depend on sensor type. Intermittent faults show missing pulses, dropped amplitude, or noisy/distorted waveform
Diagnostic algorithm
- Record code(s) and any freeze-frame data with a scan tool; note when the fault was set and driving conditions
- Visually inspect the front-left wheel area: sensor mounting, tone ring, wiring routing, and wheel bearing for play
- Unplug and inspect the sensor connector for corrosion, bent pins, or water intrusion; clean and reseal or replace connector as needed
- With connector connected, back-probe the sensor circuit and monitor live data while slowly rotating the wheel by hand; look for a steady wheel speed signal on the scan tool or waveform on an oscilloscope
- If no usable signal, remove sensor and measure resistance (for passive) or check supply/reference and output (for active) per manufacturer specs; compare with the opposite sensor
- Perform a wiggle/stress test on the harness and connector while monitoring signal to reproduce an intermittent open/short
- Check continuity between the sensor connector and the ABS module harness pin; repair any high resistance or intermittent wiring faults
- Inspect the tone/reluctor ring for missing/chipped teeth, heavy corrosion, or metal debris and correct as needed (clean, repair or replace ring)
- If wiring, connector, or sensor is faulty, repair or replace component, then clear codes and perform a road test to confirm the fault does not return
- If all wiring and sensors test good and the fault recurs, consider ABS module input fault and consult manufacturer-specific procedures before replacing the module
Likely causes
- Wiring harness damage at the wheel (flex point) or inside the wheel housing
- Corroded/loose sensor connector allowing intermittent contact
- Contaminated or displaced sensor causing variable signal amplitude
- Failed wheel speed sensor element (intermittent)
- Reluctor ring damaged or covered with debris
Fault status
Status
Intermittent/erratic signal detected from front-left wheel speed sensor circuit. ABS control module logged C2421 when the front-left wheel speed input dropped, produced missing pulses, or deviated from expected signal parameters.
Repair difficulty: Medium
Diagnostic time: 0.5–2.0 hours
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Code
C2421
HYUNDAI
C — Chassis
Motor Temperature Sensor Low Input
Views:
UK: 13
EN: 17
RU: 12
AI status
Completed
Completed
100%
Causes
- Damaged or chafed wiring in the front-left wheel speed sensor circuit
- Corroded, loose, or contaminated connector or pin at the sensor or ABS module
- Failed or intermittent wheel speed sensor (Hall-effect or variable-reluctance)
- Excessive air gap, misalignment, contamination (metal shavings, dirt) between sensor and tone/reluctor ring
- Damaged, missing or heavily corroded tone/reluctor wheel teeth
- Poor ground or power supply fault to the active sensor
Symptoms
- ABS warning lamp illuminated (may be intermittent)
- Traction/stability control warning or loss of traction control functionality
- Intermittent operation of ABS/ESC systems under braking or slippery conditions
- Inconsistent or dropping wheel speed reading for front-left when monitoring live data
- Possible pulsating brakes or reduced ABS performance during an event
What to check
- Read ABS codes and any freeze-frame/fault timestamps with a scan tool
- Monitor live wheel speed sensor values for all four corners while turning the wheels by hand and during a low-speed road test
- Visually inspect front-left sensor, wiring harness, and connector for damage, corrosion, pin damage, or contamination
- Perform a wiggle test on the wiring and connector while watching live data or using an oscilloscope to reproduce the intermittent behavior
- Back-probe connector to verify supply voltage (if active sensor) and ground integrity
- Measure sensor resistance (for passive sensors) and check AC output while spinning the wheel
Signal parameters
- Active (Hall/active) sensor: typically has a reference supply (usually ~5 V) and outputs a digital/square-wave or open-collector pulse—signal toggles between near 0 V and supply voltage as the wheel turns
- Passive (variable-reluctance) sensor: no supply; produces AC voltage proportional to wheel speed (measurable AC voltage when wheel is rotated). Low-speed AC may be ~0.1–1 Vrms and increases with speed (exact values are manufacturer-specific)
- Typical diagnostic checks: sensor resistance (passive sensor) — manufacturer spec varies; compare to opposite side and service manual values
- Signal waveform: regular pulses at consistent frequency as wheel rotates; amplitude and shape depend on sensor type. Intermittent faults show missing pulses, dropped amplitude, or noisy/distorted waveform
Diagnostic algorithm
- Record code(s) and any freeze-frame data with a scan tool; note when the fault was set and driving conditions
- Visually inspect the front-left wheel area: sensor mounting, tone ring, wiring routing, and wheel bearing for play
- Unplug and inspect the sensor connector for corrosion, bent pins, or water intrusion; clean and reseal or replace connector as needed
- With connector connected, back-probe the sensor circuit and monitor live data while slowly rotating the wheel by hand; look for a steady wheel speed signal on the scan tool or waveform on an oscilloscope
- If no usable signal, remove sensor and measure resistance (for passive) or check supply/reference and output (for active) per manufacturer specs; compare with the opposite sensor
- Perform a wiggle/stress test on the harness and connector while monitoring signal to reproduce an intermittent open/short
- Check continuity between the sensor connector and the ABS module harness pin; repair any high resistance or intermittent wiring faults
- Inspect the tone/reluctor ring for missing/chipped teeth, heavy corrosion, or metal debris and correct as needed (clean, repair or replace ring)
- If wiring, connector, or sensor is faulty, repair or replace component, then clear codes and perform a road test to confirm the fault does not return
- If all wiring and sensors test good and the fault recurs, consider ABS module input fault and consult manufacturer-specific procedures before replacing the module
Likely causes
- Wiring harness damage at the wheel (flex point) or inside the wheel housing
- Corroded/loose sensor connector allowing intermittent contact
- Contaminated or displaced sensor causing variable signal amplitude
- Failed wheel speed sensor element (intermittent)
- Reluctor ring damaged or covered with debris
Fault status
Status
Intermittent/erratic signal detected from front-left wheel speed sensor circuit. ABS control module logged C2421 when the front-left wheel speed input dropped, produced missing pulses, or deviated from expected signal parameters.
Repair difficulty: Medium
Diagnostic time: 0.5–2.0 hours
Similar codes
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