C1A64

Code

Generic C — Chassis

Rear Left Wheel Speed Sensor Circuit Fault

Brand: Generic

Type: C — Chassis

Views: UK: 7 EN: 21 RU: 8

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open or short in the wheel speed sensor wiring (connector, chafing, broken wire)
Corroded or loose sensor connector or poor ground
Failed wheel speed sensor (Hall-effect or inductive)
Damaged or missing tone ring (reluctor) or excessive air gap
Contaminated sensor (metal shavings, brake dust) or magnet damage
Faulty ABS/ESC control module or internal input circuitry

Symptoms

ABS warning lamp and/or traction/stability control lamp illuminated
Cruise control, traction control or stability assist may be disabled
ABS may activate unexpectedly or fail to activate under heavy braking
Inconsistent or zero wheel speed reading for rear left on a scan tool
Possible drivability complaints if stability systems intervene

What to check

Read stored and pending DTCs and freeze-frame data with a capable scan tool
Inspect rear left wheel area: sensor, connector, wiring harness, tone ring and wheel bearing for damage
Visually check connector for corrosion, bent pins, moisture, or loose fit
Back-probe sensor connector and monitor live wheel speed data while spinning the wheel
Perform wiggle test on harness while monitoring data to find intermittent faults
Measure sensor resistance (if passive) and compare to specification; check for short to ground or supply

Signal parameters

Passive (inductive) sensor: DC resistance typically in the hundreds to low thousands of ohms (manufacturer spec required); produces AC voltage proportional to wheel speed (millivolts at low speed, rising with RPM)
Active (Hall/VR with electronics) sensor: three-wire (Vref, GND, Signal) or two-wire with internal electronics; Vref typically ~5 V (or vehicle-specific), signal is a pulsed square/TTL-like waveform between ~0–5 V
Expected behavior: at rest a stable idle reading or zero speed; when wheel is rotated, frequency and amplitude/voltage should increase smoothly with wheel speed
Failure signatures: open circuit = infinite resistance / no signal, short to ground/power = near 0 ohms or pinned voltage, erratic waveform = intermittent connection or damaged tone ring

Diagnostic algorithm

Use scan tool: record fault code(s), freeze frame, and monitor all four wheel speed inputs simultaneously.
Clear codes, perform a controlled road or lift test and watch live data to see when/if C1A64 reappears.
Visually inspect rear left sensor, harness routing, connector and tone ring for damage, contamination or missing teeth.
Back-probe the sensor connector: verify reference voltage (if applicable), ground continuity and observe signal while spinning the wheel by hand or with a scan tool.
Measure sensor DC resistance (for passive sensors) and check for shorts to ground or battery. Replace if out of spec or open.
Check AC output of passive sensors while spinning wheel (oscilloscope preferred) and inspect waveform for amplitude and frequency proportional to RPM.
Wiggle the harness and move suspension while monitoring live data to reproduce intermittent faults; repair any chafing or broken wires.
Inspect and measure air gap between sensor tip and tone ring; correct or replace damaged tone ring or hub as required.
If sensor and wiring test good, compare with the opposite wheel sensor by swapping sensors (if identical) or test module input continuity back to ABS module.
After repair, clear codes and retest in the same conditions that originally produced the fault to confirm repair.

Likely causes

Damaged/contaminated or failed rear left wheel speed sensor
Wiring harness damage or corroded/loose connector at wheel hub
Damaged/dirty tone ring or excessive air gap from sensor
Intermittent connection caused by wheel bearing wear or hub play
Less likely: ABS module input fault

Fault status

⚠️ Status

Rear left wheel speed sensor circuit fault detected by ABS/ESC control module. Inspect sensor, wiring, connector, and tone ring. System functionality (ABS/traction control) may be reduced until fault is resolved.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours