C0399

Code

Generic C — Chassis

Wheel Speed Sensor Circuit — Intermittent/No Signal

Brand: Generic

Type: C — Chassis

Views: UK: 7 EN: 6 RU: 10

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged or contaminated wheel speed (ABS) sensor
Broken, corroded or loose sensor connector or wiring
Reluctor ring (tone ring) damaged, dirty, or missing teeth
Poor sensor-to-reluctor air gap or incorrect sensor mounting
Intermittent short/open in harness or connector
Faulty ABS/BCM module or poor module ground/power

Symptoms

ABS, traction control, or stability light illuminated
ABS/ESC interventions may be disabled or behave unpredictably
Instrumented vehicle speed may be incorrect or fluctuating for affected wheel
Intermittent fault — may appear or disappear with vibration, temperature, or movement
Possible noise or roughness from affected wheel (if bearing/reluctor damage)

What to check

Read stored/active DTCs and freeze frame data with a scan tool; identify affected wheel and conditions when fault set
Visually inspect sensor and connector at the affected wheel for corrosion, damage, and secure mounting
Wiggle test wiring and connector while monitoring live wheel speed data to reproduce intermittent signal
Inspect reluctor (tone) ring for missing teeth, rust, dents, or heavy contamination
Measure sensor resistance and compare to manufacturer specification (if passive sensor)
Measure sensor supply/reference and signal with a multimeter/oscilloscope while rotating the wheel

Signal parameters

Passive (magnetic) sensor: produces AC voltage pulses; amplitude increases with wheel speed. Typical idle/low-speed RMS may be ~0.2–1.5 V and rises with speed (varies by design).
Active (hall/magnetoresistive) sensor: produces digital/pulse or 0–5 V square wave referenced to a power supply (often 5 V or vehicle-specific); frequency proportional to wheel speed.
Frequency: increases linearly with wheel speed; at low speeds expect a few Hz to tens of Hz, rising to several hundred Hz at highway speeds.
Resistance (passive sensor): check against vehicle spec; out-of-spec or open indicates a failed sensor.
Intermittent faults often show irregular, missing, or noisy pulses on an oscilloscope rather than steady amplitude/frequency.

Diagnostic algorithm

Connect a capable scan tool, record freeze frame and live wheel speed data for all four wheels; note which wheel shows dropouts or inconsistent readings.
Visually inspect the suspect sensor, connector, and tone ring. Clean sensor and tone ring if contaminated and re-test.
Perform a wiggle test: with ignition on and monitoring live data, move the harness/connector and rotate the wheel to reproduce the intermittent reading.
Check connector pins for corrosion, bent pins, or water intrusion. Repair/replace connector or apply dielectric grease after repair.
Measure sensor resistance (for passive sensors) and compare to spec. An open or short indicates replacement.
With wheel raised and safely supported, rotate wheel and measure AC output (passive) with multimeter set to AC or use an oscilloscope for waveform; for active sensors, check supply/reference voltage and signal waveform.
Perform continuity and insulation resistance checks between sensor connector and ABS module; repair any damaged wiring or poor splices.
Inspect tone ring runout and tooth integrity; replace or repair if damaged. Check wheel bearing condition and replace if excessive play has shifted the ring/sensor gap.
If wiring and sensor test good, verify ABS module power/ground and CAN/communication; if module faults persist, consult module-specific diagnostic procedures.
After repairs, clear codes and perform a road test under the same conditions that set the code to confirm the issue is resolved.

Likely causes

Corroded/loose connector at the wheel hub causing intermittent contact
Physical damage to the sensor (impacts, contamination)
Wiring abrasion at suspension articulation points producing intermittent opens
Debris, rust or broken teeth on the tone/reluctor ring disrupting pulses

Fault status

⚠️ Status

Wheel speed sensor circuit intermittent or no signal detected. Check sensor, wiring, connectors, tone ring, and ABS module power/ground. Intermittent faults may require dynamic testing to reproduce.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours