C1A6B

Code

Generic C — Chassis

Left Rear Wheel Speed Sensor Circuit Intermittent

Brand: Generic

Type: C — Chassis

Views: UK: 13 EN: 15 RU: 10

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged, chafed, or broken sensor wiring or connector
Corroded or loose connector or pin
Faulty left rear wheel speed sensor (Hall effect or VR type)
Damaged or contaminated tone ring/reluctor (cracked, missing teeth, heavy corrosion/debris)
Intermittent poor ground or supply voltage to the sensor
Intermittent fault in ABS/ESC control module or connector

Symptoms

ABS warning lamp (and/or traction control/stability lamp) illuminated intermittently
ABS or traction control operation unpredictable or unavailable
Intermittent activation of ABS during normal braking
Possible inconsistent speedometer or cruise control issues (on some vehicles)
Fault code present for left rear wheel speed sensor intermittently

What to check

Scan for active and stored ABS/ESC codes and note freeze frame/data
Visually inspect left rear wheel sensor, connector and wiring harness for damage, corrosion, chafing, or signs of water intrusion
Check tone ring/reluctor for cracks, missing teeth, heavy rust or debris
Wiggle harness and connector while watching live data for the left rear wheel speed signal
Check for excessive wheel bearing play or suspension movement that could alter sensor gap
Verify proper connector seating and pins (no spread, corrosion or bent pins)

Signal parameters

Hall-effect (digital) sensor: square wave 0–5 V (or 0–12 V on some systems) switching between reference voltage and ground; frequency proportional to wheel speed
VR (variable reluctance) sensor: AC sine-like waveform; amplitude increases with speed (typical low-speed 0.2–4 V AC, higher speed several volts peak-to-peak)
Typical VR sensor DC resistance (varies by vehicle): approximately 500–1500 Ω (consult OEM spec)
Hall sensor supply typically 5 V or vehicle battery voltage; pull-up to Vref should be present when back-probing
Signal frequency range: 0 Hz at rest up to a few kHz depending on wheel speed; check live data for plausibility
Intermittent dropouts, noisy waveform, or sudden spikes indicate wiring/connector or sensor problems

Diagnostic algorithm

Read and record all ABS/ESC codes and live wheel speed sensor data. Note when the fault set and any related codes.
Perform a visual inspection of the left rear sensor, tone ring, wheel bearing, and wiring harness. Repair obvious damage (re-seat connector, clean corrosion, remove debris).
With ignition on (engine off) backprobe the sensor connector: for Hall sensors verify supply voltage (Vref), ground, and output toggling while rotating the wheel; for VR sensors measure AC output while spinning wheel. Use a scope if available.
Wiggle test the harness and connector while monitoring live data or oscilloscope to reproduce the intermittent behavior. Inspect connector pins for intermittent contact.
Measure sensor resistance (if VR) and compare to OEM spec. Replace sensor if open, shorted, or out of spec.
If sensor signals are good at the connector but intermittent at the module, inspect and test continuity of wiring to the ABS module (pin-to-pin resistance/shorts to ground/battery). Repair any opens or shorts, repair corroded connectors, and secure harness away from moving parts.
Inspect tone ring condition and repair/replace if damaged or contaminated. Correct excessive bearing play if present.
If wiring, sensor and tone ring check good, investigate module connector and ground circuits; consider module bench or module-level diagnostics per OEM procedures.
After repairs, clear codes and perform road test or controlled wheel rotation to confirm stable signal and that the code does not return.
If intermittent persists and all vehicle wiring and sensor verified, consider intermittent module fault and follow manufacturer module diagnostics or replacement procedures.

Likely causes

Corroded or loose wheel speed sensor connector
Chafed wiring harness at suspension pivot or near wheel
Failed wheel speed sensor
Debris or damaged tone ring producing intermittent signal
Intermittent ground at sensor or control module

Fault status

⚠️ Status

Left rear wheel speed sensor circuit intermittent — signal intermittently not detected or unstable. Check sensor, wiring, connector, and tone ring for faults.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours