If a “Reduced Steering Assist, Drive With Care” warning message recently appeared on your dashboard, you’re likely both alarmed and concerned about upcoming expensive repairs. But how serious is it really?
Keep reading to learn how steering assist works, possible causes of this message, and most importantly, how to fix it.
What is Steering Assist?
Steering Assist is a supplementary system that works alongside the power steering system. Its role is to increase the assistance provided by the power steering system using various sensors located around the vehicle. Steering Assist can help with lane centering or even semi-autonomous driving in some cases.
Many brands offer some form of steering assistance, 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 Alert with Steering Assist (Toyota), and Autopilot (Tesla).
How Does It Work?
While it sounds like a feature from a video game, the concept is actually quite similar to the autopilot you’d find in Mario Kart that prevents you from falling off the map.
Steering assist systems use different 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.
Through lane change assistance and lane centering, the vehicle detects the lines on the road that determine where your lane is. When you start to drift toward one of the lines, the power steering motors apply a slight amount of steering lock to keep you centered in your lane.
More sophisticated steering assist systems are considered semi-autonomous. There are different levels of autonomous driving. If you plan to use these systems, it’s very important that you familiarize yourself with your owner’s manual to understand the limitations of your specific vehicle.
Causes of Reduced Steering Assist
There are several common causes of reduced steering assist, and some of them might not be what you’d expect.
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1) Battery Problems
A faulty car battery or low battery voltage can cause problems with the steering assist system. These issues are typically accompanied by other warning lights you might expect to see with a faulty battery.
To fix this issue, the solution is often to replace the battery. Sometimes, the battery is dead because the alternator is faulty. A faulty alternator won’t be able to charge the battery sufficiently, which might require you to get a jump start.
2) Faulty Steering Assist Module
The steering assist module controls the operation of the steering assist system. A problem with this particular computer would make the steering assist system unusable, and the only solution would be to replace the module.
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3) Code Stored in the Steering Assist Control Module
Depending on the code, a code stored in the steering assist module can cause the system to shut down, even if the system is functioning normally. You can try clearing the codes to see if the system returns to normal operation.
Note that clearing codes often doesn’t fix the root cause of the problem, especially if the issue is intermittent. If the error code reappears, it’s best to start doing some diagnostic work to see what’s happening with the steering assist system.
4) Inclement Weather
The Steering Assist system relies on different sensors distributed throughout the vehicle, some of which may be cameras or optical sensors. If the view of these cameras is obstructed by heavy rain, fog, or snow, they may not be able to see the lines on the road.
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Inclement weather can disrupt all kinds of driving assistance systems. It’s important to remain vigilant at all times while operating the vehicle, even if some level of semi-autonomous driving is offered in your vehicle.
The solution is often as simple as cleaning all the external sensors that provide data for steering assistance. Your owner’s manual should specify where these sensors are located.
5) Thermostat Problem
While it may not seem related, some GM models will display the “Reduced Steering Assist, Drive With Care” message when the thermostat is stuck open. You can tell your thermostat is stuck open because your coolant temperature gauge indicates the engine is cold, even after driving for 20 minutes or more.
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This issue is often also accompanied by a P0128 code – Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature).
There is a Technical Service Bulletin (TSB) for this problem and you should be able to have it repaired 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 seems unrelated? To quote the bulletin: "The reduced steering assist issue is caused by an invalid coolant temperature signal from the ECM. The steering module looks for a valid coolant temperature so it can compensate for cold, thick grease. When grease cools, it becomes thicker and harder to move. This can result in a heavier than normal steering feel. The steering module, when it thinks it's cold due to the coolant temperature value, provides extra assistance to account for the heavier conditions. Since the coolant value on the CAN bus became invalid, this function of the steering module became inoperative."
If your vehicle is under warranty, this issue should be covered at no cost to you. This particular issue should be covered by your powertrain warranty, even if your bumper-to-bumper warranty has expired.