The torque sensor is built-in the pinion shaft assembly, using a magnet and an AMR sensor to detect steering wheel torque forces. The pinion shaft assembly consists of the input shaft, the torsion bar, the pinion gear, and the torque sensor unit.

The AMR sensor within the torque sensor unit measures changes in the magnetic phase of the magnet attached to the input shaft.

As the driver operates the steering wheel, the input shaft rotates, twisting the torsion bar and relatively offsetting the input shaft to the pinion gear. This changes the magnetic phase of the input shaft in relation to the AMR sensor. The AMR sensor then registers the change in lines of magnetic force as magnitude of twist in the torsion bar.