C065F

Code

Generic C — Chassis

Left Rear Wheel Speed Sensor B Circuit/Open

Brand: Generic

Type: C — Chassis

Views: UK: 19 EN: 28 RU: 25

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open or broken wiring in the left rear wheel speed sensor circuit
Corroded, loose or disconnected sensor connector
Failed wheel speed sensor (internal open)
Damaged or missing tone ring/reluctor on the wheel/hub
Short to battery or chassis ground at the sensor harness
Faulty ABS/ESC control module or poor module grounding

Symptoms

ABS and/or traction/stability control warning light illuminated
Loss of rear ABS or limited braking/traction control functionality
No or erratic left rear wheel speed reading in scan tool live data
Possible limp/limited mode for stability systems
In some vehicles, inconsistent vehicle speed/traction behavior during low-grip conditions

What to check

Read stored ABS/ESC codes and freeze-frame data with a scan tool; note conditions when code set
View live data: compare left rear wheel speed to other wheels at rest and while rolling
Visual inspection of left rear sensor, connector, wiring harness and tone ring for damage or contamination
Wiggle test: move harness and connector while watching live data or monitoring for intermittent change
Check connector for corrosion, bent pins, water intrusion or poor fit
Measure sensor resistance/continuity with a multimeter and check continuity to ABS module connector

Signal parameters

Passive (two‑wire) sensors: show AC voltage while wheel turns; amplitude increases with speed (typical tens of mV to volts depending on speed and sensor type)
Active (three‑wire/Hall) sensors: produce a digital/square wave signal referenced to 5V (or vehicle reference) with frequency proportional to wheel speed
Typical DC resistance for passive sensors often falls in a broad range (hundreds to a few thousand ohms); an open circuit shows infinite resistance
At rest, a proper sensor will show defined resistance (passive) or a stable reference supply and a valid idle signal level (active)
When code is set: signal may be open (infinite resistance) or no signal output while wheel rotates

Diagnostic algorithm

Verify the code with a scan tool and record freeze-frame data; clear codes and attempt to reproduce to confirm persistence.
Inspect the left rear wheel area: sensor, mounting, tone ring/reluctor, and connector for physical damage, contamination or missing teeth.
Check the connector: unplug and inspect pins for corrosion, bent pins, or pushed-out terminals; reconnect firmly.
Identify sensor type (2‑wire passive or 3‑wire active). For passive sensors measure DC resistance across sensor leads; an open reading indicates a failed sensor.
With connector connected, backprobe signal and reference/ground circuits. Rotate the wheel by hand or road test while monitoring with a multimeter or oscilloscope: passive sensors produce an AC waveform, active sensors produce a square wave or switching signal.
If no signal, check continuity from the sensor connector to the ABS module connector and to ground; repair any open or high-resistance wiring.
Wiggle the harness and connectors while monitoring live data to detect intermittent faults; repair chafing or broken wires found.
Inspect tone ring for missing/broken teeth, heavy corrosion, or separation from hub; replace or refit as required.
If wiring and sensor check good but fault persists, verify ABS module power and ground circuits and inspect module connector for damage; consult manufacturer guidance before replacing module.
After repairs or replacement, clear codes and perform a road test to confirm the left rear wheel speed signal is present and the fault does not return.

Likely causes

Damaged wiring or broken connector at left rear wheel (most common)
Failed wheel speed sensor (water ingress/corrosion)
Missing or damaged tone ring on the hub/axle
Connector contamination or broken pins

Fault status

⚠️ Status

Left Rear Wheel Speed Sensor B Circuit/Open — no valid wheel speed signal detected from left rear sensor; ABS/ESC function for that wheel may be disabled.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours