Your receiver might be bad. When the receiver goes sometimes channels don’t work, or they exhibit some other undesirable behavior. Got another rig you could try out the servo in? Does the throttle work? Try swapping them around, steering into channel 2 and esc into channel 1, this is assuming throttle works currently. You could test out the steering when plugged into channel two with the throttle on the remote and the esc on the steering.