Chassis, generic

C066B Right Rear Wheel Speed Sensor B Correlation

Check engine lightUsually off
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

The second right rear speed value is electrically fine but disagrees with its references. No carmaker documents C066B or its limits. A Ford patent shows a check that suits a driven rear axle: the right rear speed is calculated as twice the output shaft speed divided by the axle ratio, minus the measured left rear speed. If measured and calculated values differ beyond a tolerance on consecutive passes or for more than 0.2 s, the fault is registered, and the calculated value stands in meanwhile. The tolerance can be tightened with lateral acceleration, and the side under more load gets the closer look. Bosch describes a similar estimate from the three other wheels, validated against the gearbox output. Wrong tyre sizes or a damaged encoder can trigger such a mismatch.

Likely causes

Mismatched tyre size or tread depth at the right rear
Encoder with missing or extra pulses
Axle ratio or tyre data in the module not matching the vehicle

Symptoms

  • Warning after a fast or long drive
  • Traction or stability functions temporarily reduced

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–900
Time0.5–3 h

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

Parts involved

rr wss brr wsstone ring

Related codes

C0667C066AC066CC0517C0664

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