quote:The steering input is derived from the torque sensor in the steering column and speed is from the VSS but might be translated by the BCM in the serial port or through the CAN communication. This is very difficult for a backyard wrench turner to address this need. To accomplish this a microprocessor needs to be programmed to fake the BCM signal."
I strongly suspect that is what the after-market units using a potentiometer are doing.
To do the assist properly, two inputs are needed:
tire resistance, measured by sensing the torque needed to rotate steering wheel. This is done internally on the EPS shaft.
level of assist, dependent on vehicle speed and controlled by an external-to-the EPS unit VSS input.... or the potentiometer through a suitable controller.
As for the internal torque sensor, this little YouTube video with a cut-away unit helps in displaying the internal workings of an EPS.
https://youtu.be/H-kBebxMPrw
Larry
