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How Does Electric Power Steering Work?

How Does Electric Power Steering Work?

What is Electronic Power Steering and How Does it Work?

Let’s pretend for a moment that you have a time machine, and it’s set for a century ago. You hop in and find yourself in the driver’s seat of an antique Ford or Studebaker with the engine already idling. You put the car in gear and get ready to go, but something is immediately apparent: this car is very, very difficult to steer!

That’s because early automobiles were not equipped with power steering systems, so low-speed action like turning a corner or parking in specific spot were extremely difficult. While automobile designs were being improved upon from the moment they were created, it would still be another half century before the first versions of power steering systems were widely available. Luckily for us, this cycle of ingenuity is still going on today and modern vehicles are only becoming easier to maneuver, safer and more fun to drive.

A Powerful History

Rudimentary steering assistance systems designed and patented by Francis Davis were used in some General Motors vehicles in the 1920s, as well as large trucks and armored vehicles during World War II. By the early 1950s, Davis’ patents had expired, and Chrysler started using his designs to work on a system called “Hydraguide”. Once this system debuted on the 1951 Chrysler Imperial, driving in America was never the same.

By 1953, several other car manufacturers had followed suit, incorporating power steering to their designs, and by 1960, power steering had grown in popularity with more than 3.5 million cars outfitted with it.

These early power steering systems were hydraulic systems. Hydraulic systems transfer force by compressing fluids. In the case of hydraulic power steering, the system engages when you turn your wheel and power steering fluid is pumped from a reservoir into the system via pressurized lines.

If the Pontiac Fiero was not discontinued in 1988, it would have been the first domestic vehicle to feature electronic power steering. In the early 1990s, GM revived their EPS design for their first-ever electronic vehicle, the EV1. Also known as EPS or EPAS (Electronic Power Assist Steering), this system featured an electrically driven pump with a normal rack and pinion steering gear. This design was expanded upon and improved vastly during the next two decades.

Steering Into the Future

Modern Electric Power Steering systems consist of several cooperating components. These systems use a network of sensors to collect and relay data used to assist in turning and steering the vehicle smoothly. These parts are located throughout the steering column down to the steering rack. They include:

The steering wheel position sensor, also known as a steering angle sensor, sits on the steering column and senses the direction the driver is turning the steering wheel. The steering torque sensor detects the amount of force applied when turning the wheel. It is found on vehicles with a rack and pinion style system and sits at the point where the rack connects to the steering column.

The data gathered from the steering wheel position sensor and the steering torque sensor is logged on the vehicle’s ECM or Electronic Control Module and sent to the steering control unit or the steering control module. The module is now aware of what direction the steering wheel is turning and how hard. The steering control module is connected to the electric motor, which powers the gears needed to move the rack laterally depending on the direction the driver is turning.

Ford truck EPS rack

Is My Electric Power Steering Broken?

Whether you’ve hit a particularly rough pothole or there’s just a part of your EPS system that has malfunctioned, power steering issues will likely be obvious. In some cases, your vehicle may suddenly become very difficult to steer or you may notice:

  • EPS Warning light illuminating on the dash
  • Vehicle pulls hard in one direction
  • Squealing noise from the power steering motor
  • Vibrations coming from the rack

If you suspect you are having power steering issues, turn on your hazard flashers and, when it is safe to do so, maneuver your vehicle to a safe area where you can get out and inspect it. If your vehicle is equipped with electric power steering, you likely won’t notice any leaking fluids or hoses, so use a diagnostic scan tool or code reader to see what may be failing. Because steering a car is extremely difficult without power assist, towing is the safest option.

When it comes to at-home electronic power steering repairs, you can rest assured that NAPA carries all the tools and parts you need for a successful job. While this repair is involved for most home mechanics, a little research and the right tools can go a long way. But if you don’t feel confident enough or, like most of us, you don’t have time, find your nearest local NAPA Auto Care center! Make an appointment today and let our friendly and knowledgeable experts steer you back on the road in no time.

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More than 90 years ago, the National Automotive Parts Association ("NAPA") was created to meet America’s growing need for an effective auto parts distribution system. Today, 91% of do-it-yourself customers recognize the NAPA brand name. We have over 6,000 NAPA Auto Parts Stores nationwide serving all 50 states with a unique inventory control system that helps you find the exact part that you need.

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