A warehouse logistics center reported a bizarre fault on a Hangcha CPD25 2.5-ton electric forklift. While driving, the steering wheel would suddenly "lock up" (become extremely stiff) for 3-4 seconds, and the dashboard would flash a "Steering Fault" code. The operator could turn the key off and on to reset it, but it happened 5-6 times per shift, creating a safety hazard in the narrow aisles.
The technician connected the diagnostic tool to the Electronic Power Steering (EPS) controller. The stored fault code was "C1021: Steering Angle Sensor Signal Loss." Unlike traditional hydraulic steering, this EPS system uses a sensor on the steering column to detect the driver's input and a position sensor on the rear axle.
He first inspected the steering column torque sensor. The connector was tight. He then moved to the rear axle. The EPS system uses a "pinion gear" on the motor that meshes with a sector gear on the axle. He checked the mechanical backlash, which was within spec. He then focused on the "Steering Angle Position Sensor" mounted on the rear of the axle. This sensor tells the controller where straight ahead is.
He found that the sensor mount was loose. When the forklift hit a bump or turned sharply, the sensor would physically shift on its bracket. Because the sensor position shifted, the controller saw a discrepancy between the steering wheel angle (input) and the rear wheel angle (output). The computer interpreted this mismatch as a "system runaway" and triggered a safety lockout (stiff steering) to prevent an accident.
The repair involved aligning the position sensor to "neutral" (centering the wheels first) and tightening the mounting bracket to the specified torque with thread-locking compound. The sensor connector was also cleaned and reseated. After the repair, the technician performed a "Steering Calibration" via the diagnostic tool to reset the zero-point. The intermittent lock-up issue was permanently resolved, restoring confidence for the operator.
