A reach truck in a freezer warehouse was throwing an intermittent "Steer Angle Sensor Fault" that completely locked the steering. The technician replaced the steering angle sensor and the wiring harness, but the fault returned a week later.
The steer angle sensor on a reach truck uses a Hall-effect pickup mounted to the steer axle frame, reading a toothed reluctor ring mounted to the steering column. When the truck hit a bump or a dock plate, the steering would lock up, and the dash would flash the fault code.
We jacked the steer axle up and pry-barred the steering knuckle. There was massive play in the kingpin bushings. When the truck was stationary, the sensor and the ring were properly aligned. But when the truck hit a bump, the worn bushings allowed the steering knuckle and the column to shift axially by over 1/8 of an inch. This tiny mechanical shift pushed the reluctor ring away from the stationary Hall-effect sensor. The controller lost the signal, panicked, and locked the steering. The $3,000 electrical repair was a waste of money; replacing the$30 brass kingpin bushings eliminated the axial play and fixed the sensor fault permanently.
