“Steering Assist is Reduced, Drive with Care” (Causes and How to Fix)

If a “Steering Assist is Reduced, Drive with Care” warning recently popped up on your dash, you’re probably both alarmed and concerned about expensive repairs in the near future. But how serious is it really?

Keep reading to learn how steering assist works, the possible causes of this message, and most importantly, how to fix it.

What Is Steering Assist?

Steering Assist is a supplemental system that works alongside the power steering system. Its job is to augment the support provided by the power steering system using various sensors around the vehicle. Steering Assist may assist with lane centering or even semi-autonomous driving in some instances.

Many makes provide some sort of steering assist, and this feature may be called different names depending on the manufacturer.

Steering Assist is also known as Lane Keep Assist (GM, Jaguar, Land Rover, Mazda, Subaru), Road Departure Mitigation (Honda/Acura), Steering Intervention, Lane Departure Warning with Steering Assist (Toyota), and Autopilot (Tesla).

How Does It Work?

hands off steering wheel

Although it sounds like a feature in a video game, the concept is actually quite similar to the autopilot you would find in Mario Kart that keeps you from falling off the map.

Steering Assist systems use various sensors around the vehicle to determine where the vehicle is in the lane and where the driver intends to go. These sensors may include cameras, engine temperature, a yaw sensor, and a steering angle sensor.

With lane departure and lane centering assistance, the vehicle detects the lines on the road that determine where your lane is. As you start to veer toward one of the lines, motors in the power steering apply a small amount of steering lock to keep you centered in your lane.

More sophisticated Steering Assist systems are considered to be semi-autonomous. There are various levels of autonomous driving. If you wish to use these systems, it is very important that you familiarize yourself with your owner’s manual so you understand the limitations of your specific vehicle.

Causes of Reduced Steering Assist

There are a few common causes of reduced Steering Assist, and some of them are not what you might expect.

1) Battery Issues

old battery

A bad car battery or low battery voltage can cause issues with the steering assist system. Typically these will be accompanied with another warning light that you might expect to see with a bad battery.

To resolve this issue, often the solution is to replace the battery. Sometimes the battery has gone flat because the alternator is bad. A bad alternator will not able to charge the battery sufficiently, which could leave you asking for a jump.

2) Bad Steering Assist Module

The Steering Assist module controls the operation of the Steering Assist system. A problem with this particular computer would render the Steering Assist system inoperable and the only fix is to replace the module.

3) Stored Code in the Steering Assist Control Module

Depending on the code, a stored code in the Steering Assist module may cause the system to turn off, even if the system is otherwise functioning normally. You could try clearing any codes to see if the system resumes normal operation.

Note that clearing codes often does not resolve the root cause of the issue, particularly if the problem is intermittent. If the trouble code returns, it’s best to start doing a bit of diagnostic work to see what’s going on with the Steering Assist system.

4) Inclement Weather

The Steering Assist system relies on various sensors throughout the vehicle, some of which may be cameras or optical sensors. If the view of these cameras are obscured due to heavy rain, fog, or snow, they may not be able to see the lines on the road.

Inclement weather may interfere with driver assist systems of all kinds. It’s important to stay alert behind the vehicle at all times, even if some level of semi-autonomous driving is offered in your vehicle.

The fix is often as simple as wiping clean any exterior sensors that provide the data for Steering Assist. Your owner’s manual should specify where these sensors are located.

5) Thermostat Problem

thermostat replacement

Although seemingly unrelated, certain GM models will throw “Steering Assist Reduced Drive With Care” message when the thermostat is stuck open. You can tell your thermostat is stuck open because your coolant temperature gauge will show that the engine is cold, even after you’ve been driving for 20 minutes or more.

This issue is often also accompanied with a P0128 code – Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature).

There is a Technical Service Bulletin (TSB) out for this issue and you should be able to get it fixed at the dealership. The service bulletin number for this particular issue is 17-NA-158.

Why would the Steering Assist system be affected by the coolant temperature, which is seemingly unrelated? To quote the bulletin:

"The Steering Assist Reduced issue is caused by an invalid coolant temp signal from the ECM. The steering module looks for a valid coolant temp so it can compensate for cold and thick grease. As grease gets cold, it becomes thicker and harder to move. This can cause a heavier than normal steering feel. The steering module, when it thinks its cold due to the coolant temperature value, provides extra assist to support heavier condition. Since the coolant value on the CAN bus went invalid, this function of the steering module went inoperative."

If your vehicle is under warranty, this issue should be covered at no cost for you. This particular issue should be covered by your powertrain warranty, even if your bumper-to-bumper warranty has expired.


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