C0656 Left Front Wheel Speed Sensor B Correlation

C0656 flags a mismatch between the B signal at the left front hub and the values it is checked against, typically sensor A on the same hub, while the circuit itself tests good. No carmaker publishes this code or its limits. Two patent designs show what such a comparison can catch. Continental Teves placed two magnetoresistive paths of different sensitivity in one housing; a comparator inside the sensor checks whether both deliver the same frequency, because a disturbed path can flip and even double the reading. Audi proposed pairing an active Hall sensor with a passive inductive one on the same pulse wheel, so that a supply failure cannot silence both. Likely causes: a damaged encoder, a sensor sitting too far from its encoder, mixed-up parts.

Likely causes

Symptoms

• Warning for brake or driver assistance system
• Automated or redundant brake functions withdrawn, ABS usually still active

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: patents.google.com, patents.google.com.