Shaky Steering Wheel While Driving? Could it Be a Bad Steering Torque Sensor?
What Is May Not Seem As It Is After All
Your steering wheel is shaking while you're driving down the road. You find after having the usual suspects checked (tires, front end and front end parts) that nothing is loose or malfunctioning. As you're scratching your head wondering what the hell could possibly be wrong, the technician discovers something that most people may miss. He tells you that you may need to replace the Steering Torque Sensor.
Now in my few years of being a mechanic I had the same opportunity, after doing research on Alldata and other "online manual" type sites, to discover this very same problem. And, like some other tech's who may have discovered this problem, I was more than likely asking the same question that came to mind ... "What's a torque sensor?"
Whether you went to school for auto repair or you are a 20 plus year veteran tech, in this business you'll always come across something new. The car manufacturers are developing technologies a lot faster than the techs are discovering them. In most cases the technician won't learn about a new system or update (unless they are taking classes on a regular basis to keep up with the technology) until they have to do some kind of work on that new system or update. Thus was my case.
After test driving the car and verifying that it wasn't anything tire or front end related I jumped on the research train and determined that the symptoms all seemed to rationally point to the torque sensor and it's apparent malfunction. While doing research for this article I discovered that GM has or had a recall on this topic. I should also state that it was GM vehicle I was working on for this problem, although I don't believe at the time there was a recall.
Uhhhhh ... What's Missing?
If you're the kind of car owner who likes to do their own basic maintainence on their vehicle (check/change oil, fluids, minor repairs like tune-ups or minor component replacements) or the kind of person who takes their car in for regular maintainence and own a newer vehicle (around 2006 and up), you may have noticed that finding the power steering reservoir just got a lot harder. That's because most newer cars no longer have one to check. Many of today's cars now have Electric Power Steering or EPS.
Electric power steering works with the use of several sensors and an electric motor mounted on the steering shaft under the dashboard. The steering sensor measures how far the steering wheel is turning. The torque sensor tells the steering assist motor how much power or "assist" to apply to the steering shaft depending on how far you turn the steering wheel left or right.
One Important Thing to Remember
Most technicians who do alignments on today's newer vehicles have come across the message on the alignment machine stating that the use of a scan tool may be necessary after completing the front end portion of the alignment. There is a reason for this.
The torque sensor needs to reference a "center", not only for itself, but for the steering wheel. This is important because when you're aligning the front wheels to a straight position, you're ONLY moving the wheels striaght. While doing an alignment the steering wheel is secured from moving by a wheel lock tool used to keep the steering wheel straight while aligning the wheels. The steering wheel not moving means the shaft isn't moving either, hence, the sensor isn't moving. At this point, the torque sensor doesn't "know" what is considered to be "center".
This is important because if the sensor isn't realizing the center point then you may not get a true return to center on the steering wheel. After you finish your turn and let go of the steering wheel do you notice the steering wheel kind of "knows" where center is? Even in cars with traditional hydraulic steering, this is no accident. There is a lot of physics involved in the explanation for this, but we're not going to get into that. Just know that with an electric system there needs to be a point of origin or things get really nutty, really fast.
So once you've replaced the sensor and/or finished the alignment or both, it's time to grab the scan tool. One scan tool I've used in the past that works well is the Snap-On Solus Ultra.
Going through the menus on the scan tool, you'll find the program you'll need to calibrate the torque sensor. Proceed through the calibration and double check everything is kosher by driving the car to confirm the steering wheel is striaght, the car drives straight, and the shaking is gone.
Update April 2015
I just had the opportunity to do another one of these sensor replacement jobs. Same type of steering column ... different car. My first replacement was on a 2006 Chevy Malibu Maxx. This most recent one was a 2009 Pontiac G6. I discovered that you don't have to remove the steering wheel. I highly recommend still removing the airbag module just for safety sake however. I also discovered that the GM recall on this covers, mostly, a loss of power steering from the failure of this sensor which was the case on the 2009 G6.
So ... on to the update. I just had a 2008 Buick Enclave show up at the shop the other day. The Traction Control Light was on and the customer was complaining of a slight vibration in the steering wheel. Upon scanning the light and researching the code I found, on the Buick Enclave, the Traction Control light indicates a problem with the sensor. Also, now I think they call this sensor the steering angle sensor.
This can be confusing on the Enclave because there are about 4 different sensors on the steering column that work motors that perform different functions. The column has a sensor for the steering tilt motor, one for the telescope motor, an angle sensor and a switch (among about a million other things they can cram on a steering column). I looked into ordering the sensor and was informed that they only had one component available for replacement on the steering column for the Enclave and that if this wasn't the component I needed then my only other option would be to replace the entire steering column.
I can't say for sure that this is absolutely the only option for the Enclave, but I'm learning that not all of the GM vehicles with electric power steering have the same set up. You may be able to find out if your car falls under the recall by going to the GM site and entering your vehicle's VIN number or calling your local GM Dealer and giving them the VIN number to check for you.