C0123

Code

Generic C — Chassis

Right Rear Wheel Speed Sensor Circuit — Signal Fault

Brand: Generic

Type: C — Chassis

Views: UK: 17 EN: 23 RU: 17

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged or contaminated wheel speed sensor
Broken, corroded or disconnected wiring/connector at the sensor
Damaged tone/reluctor ring (missing teeth, heavy rust, debris)
Incorrect sensor air gap or misalignment
Bad wheel bearing or excessive play affecting sensor signal
Faulty ABS/traction control module or poor ground

Symptoms

ABS warning lamp illuminated
Traction/stability control light or reduced function
Irregular or jumping vehicle speed or ABS activation
Reduced vehicle stability/traction control performance
Stored ABS-related fault codes for wheel speed
Occasional intermittent ABS behavior under braking

What to check

Read freeze frame and live wheel speed data with a scan tool to confirm the right rear signal
Visual inspection of right rear sensor, connector, harness and tone ring for damage, corrosion or debris
Check connector pins for corrosion, bent pins, or water ingress and verify secure mating
Measure sensor resistance with multimeter (when applicable) and compare to spec
Back-probe connector and measure signal at wheel with ignition on and wheel rotated (use scan tool or scope)
Wiggle harness and spin wheel to try to reproduce the fault (intermittent)

Signal parameters

Passive (variable reluctor) sensors: DC resistance typically ~500–2000 ohms (vehicle-specific) — generates AC sine wave when wheel turns; low-speed amplitude >0.1–0.5 V AC, rising with speed
Active (Hall/effect) sensors: 5 V reference supply, ground and digital square wave output ~0–5 V (or open-collector pulsed signal referenced to module); frequency increases with wheel speed
Expected wheel speed data: right rear wheel speed should track other wheel speeds and increase smoothly with wheel rotation
Typical waveform: clean sine (passive) or square pulse (active) with consistent amplitude and timing — excessive noise, dropouts or no signal indicate fault

Diagnostic algorithm

Use a scanner to confirm C0123 and view live data: compare right rear wheel speed to other wheels at low vehicle speed or when spinning wheel.
Perform a visual inspection: check sensor, tone ring, hub area for physical damage, debris, rust or missing teeth. Clean tone ring if contaminated.
Inspect connector and wiring: unplug the sensor, look for corrosion, water ingress, broken wires, damaged insulation and ensure connector mates firmly.
Measure sensor resistance (for passive sensors) across sensor pins and compare to vehicle specification. Replace if open or out-of-range.
Check power/ground (for active sensors): back-probe connector with ignition on. Verify reference voltage (usually 5 V) and good ground continuity.
With wheel safely raised and supported, spin the wheel and observe sensor output with oscilloscope (preferred) or multimeter AC measurement. Look for clean waveform and amplitude.
Wiggle test: while monitoring signal, wiggle harness and connector to reproduce intermittent faults. Inspect flex points and body/chassis ground routing.
Inspect wheel bearing and hub: excessive play or metal debris on tone ring can distort the signal—repair/replace as required.
If wiring and sensor test good but code persists, check continuity between sensor connector and ABS module pins; repair any opens/shorts.
If all wiring and sensor checks pass, consider ABS module fault and proceed to module-level diagnostics or consult manufacturer procedures before module replacement.
After repair, clear codes and perform road test and re-scan to confirm the fault does not return.

Likely causes

Corroded/disconnected sensor connector or wiring
Damaged sensor (impact, contamination) or wrong replacement
Reluctor ring damaged, missing teeth or contaminated
Sensor air gap too large or mispositioned
Intermittent wiring harness break (inside loom or flex point)
Faulty ABS module (less common) or poor ground

Fault status

⚠️ Status

Right Rear Wheel Speed Sensor circuit — signal fault detected. Wheel speed signal missing, intermittent, out-of-range or noisy; ABS/traction control system may be disabled or limited.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2 hours