C0654

Code

Generic C — Chassis

Left Front Wheel Speed Sensor B Circuit High

Brand: Generic

Type: C — Chassis

Views: UK: 30 EN: 54 RU: 42

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ABS warning lamp and/or traction control (TCS/ESC) lamp illuminated
Loss of ABS or traction control functionality; ABS may activate unnecessarily or not at all
Wrong or no left front wheel speed reading on a diagnostic scan tool
Possible speedometer or cruise control faults (if tied to wheel speed data)
Intermittent braking oddness or traction control intervention

Read ABS/traction control codes and freeze frame data with a scan tool; note vehicle speed and ignition state when code set
Visually inspect left front sensor, connector, wiring, and tone ring for damage, contamination, or missing teeth
Wiggle test the harness while watching live sensor data for intermittent changes
Backprobe the sensor connector and measure signal voltage with ignition ON (and engine off as applicable)
Check continuity between sensor ground and chassis ground and resistance between signal and battery (+) with power off
Check for short to battery: measure continuity from signal wire to battery positive with ignition OFF

Hall‑effect sensor (most common): digital square wave; logic levels typically 0–5 V (some systems use 0–12 V). Nominal idle/high states ~0 V and ~5 V. Frequency increases with wheel speed.
Variable reluctance (VR) sensor: AC voltage; low speeds produce small AC (0.1–1.5 VAC), higher speeds produce larger amplitude (several volts peak).
Circuit high condition: measured signal higher than expected pull‑up (approaching battery voltage, e.g., >4.5 V on 5 V systems or near 12 V on 12 V circuits)
Frequency: proportional to wheel RPM (e.g., tens to thousands of Hz depending on vehicle speed and tone ring tooth count).

Verify the code with a scan tool. Clear codes and attempt to re-create; note freeze frame data.
Visually inspect left front wheel area: sensor, tone ring, mounting, connector, and harness routing for damage or contamination.
With ignition ON (engine off), backprobe the sensor connector: measure signal wire voltage relative to ground. Compare to expected reference voltage for the sensor type.
Check continuity and resistance of sensor wiring from the connector to the ABS module; check for short to battery and short to ground (power off).
If sensor is VR type, spin the wheel and measure AC voltage or use an oscilloscope to confirm waveform and amplitude; for Hall sensors, check square wave output while rotating.
Wiggle the harness/connector while monitoring live data to find intermittent shorts or opens.