Q: 2010 Ford Fusion Advance trac service light on and Rack

The advancetac service light refers to the vehicles traction control system. The traction control system monitors the steering and stability of the vehicle and engages when loss of traction has been detected. This is done by the use of electronic sensors at each of the four wheels that communicate with the Powertrain Control Module (PCM) regarding steering performance and stability in adverse weather conditions. The traction control system works by reducing engine speed and determining which wheel to apply brake pressure to in order to prevent the vehicle from sliding. The anti-lock braking system and the traction control system work together to maintain the stability of the vehicle. The computer uses this information received from electronic sensors regarding the rotational speed of each wheel, the horizontal motion of the vehicle, and the vertical motion of the vehicle to determine how to direct the traction control system or the anti-lock braking system to best control the vehicle when needed. When this warning indicator light comes on in the dashboard, this could be an indication of several issues such as faulty wheel speed sensors, a faulty steering angle sensor, a faulty rotational speed sensor or a problem with the steering rack. In some cases, the traction control system may simply need to be reprogrammed. In addition, when any of these symptoms are detected, some vehicles may go into limp mode rendering the vehicle unable to accelerate beyond about ~30mph.

The rack and pinion gear set does two things: It converts the rotational motion of the steering wheel into the linear motion needed to turn the wheels. It also provides a gear reduction, making it easier to turn the wheels by the use of reduction gears where the steering shaft connects. This system uses a torsion bar driven valve to direct and relieve pressure in a cylinder. When the steering wheel is not being turned, the steering valve is at rest. In this position fluid flows around the valve and out to the reservoir which is where the power steering fluid resides when not at work. Slight pressure also enters both sides of the assist cylinder. Because pressure is equal on both sides of the piston nothing occurs when the wheel is straight ad no assistance is need to turn the wheels either way. Occasionally you’ll notice that your steering wheel will make jerking movements or sudden turns to the left or right when not directed by you. This is typically the sign of loose bearings in the steering rack and the result of the steering rack literally moving without input. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.