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GMC Acadia Steering Assist Reduced (Solved)

Being a seasoned GMC Acadia owner, I’ve encountered the perplexing message “Steering Assist Is Reduced Drive With Care” several times.

With this experience in mind, I’ll guide you through the twists and turns of understanding and navigating this problem.

The “Steering Assist Reduced, Drive with Care” warning in GMC Acadia often comes from an incorrect coolant temperature signal from the ECM. Diagnose for a P0128 fault code, replace any faulty parts, typically the thermostat or coolant sensor, and then clear the error codes.

What Does “Steering Assist Reduced” Mean?

The “Steering Assist Reduced” message indicates an issue within the vehicle’s power steering system. The Acadia uses an electric power steering system, designed to adjust the level of assist based on driving conditions and one of these conditions is the engine coolant temperature.

Why does it care about temperature, you might ask? Well, the chillier it gets, the thicker the steering system’s grease becomes, making steering a bit like trying to wade through a pool of peanut butter. The system compensates by giving you some extra muscle – the “assist” in question.

A Common Misstep

Here’s where many of us – including myself initially – trip up. We see “steering assist” and jump to the conclusion that it’s an issue with the steering gear.

This misinterpretation can lead you down a costly path of unnecessary steering gear replacements that do nothing to fix the issue.

Identifying The Actual Problem

The real troublemaker is not the steering gear but the Engine Control Module (ECM). This crucial component, which governs the engine’s functions, sends an inaccurate coolant temperature signal.

The erroneous information confuses the steering module, preventing it from adjusting the steering assist appropriately, which triggers the “Steering Assist Reduced” message.

How To Fix The “Steering Assist Reduced” Warning Message

Step 1: Verify the P0128 fault

To start, use an OBD-II scanner to confirm the presence of the P0128 code. The OBD-II scanner can be plugged into your vehicle’s OBD-II port, typically located under the dashboard.

Once the scanner is connected, it will communicate with your car’s computer and confirm if the P0128 code is present. This fault is often the underlying cause of the “Steering Assist Reduced, Drive with Care” warning message

Step 2: Check the Coolant Temperature Sensor

The coolant temperature sensor, which monitors the engine’s coolant temperature and reports it to the ECM, may be malfunctioning.

To check this sensor:

  1. Locate the coolant temperature sensor. It’s usually positioned near the thermostat housing, where the top radiator hose connects to the engine.
  2. Once you’ve found the sensor, visually inspect it for any obvious signs of damage or corrosion.
  3. If no visible damage is detected, the sensor can be tested using a digital multimeter. The resistance of the sensor should change with temperature. A service manual for your specific vehicle can provide the exact resistance values for different temperatures.

Step 3: Check the Thermostat

If the coolant temperature sensor is in good condition, the next step is to check the thermostat.

The thermostat controls the flow of coolant through the engine to maintain optimal operating temperature. If the thermostat is stuck open, it could cause the engine to run cooler than it should, triggering the P0128 code.

  1. With the engine cold, start the vehicle and feel the upper radiator hose. It should be cool to the touch.
  2. As the engine warms up, the upper radiator hose should stay cool until the engine reaches operating temperature. At that point, the thermostat should open, and the hose should quickly become hot as coolant starts flowing through it. If the hose warms up gradually or is warm from the start, it’s likely that the thermostat is stuck open.

Step 4: Repair as Needed

If you’ve identified a faulty coolant temperature sensor or thermostat, the faulty component should be replaced. Both are relatively inexpensive parts, but if you’re not comfortable replacing them yourself, it’s best to have the repair done by a professional.

The last time I got this warning message on my GMC Acadia, I had to replace the thermostat and while the parts only costs a few hundred bucks, the dealership asked me for $1200 to replace it.

I thought it was way too expensive, so I took the matter into my own hands (I regret it). Despite dealing with similar replacements in my day-to-day work, it wasn’t easy at all on the GMC Acadia. It took almost 6 hours!

Unlike most cars, the thermostat on the GMC Acadia is located behind some major components, which makes its replacement such a headache-inducing task.

Step 5: Clear the Error Codes

Once the repair is done, you can use the OBD-II scanner to clear the error codes, including the P0128 and the Steering Gear U0401 error.

After clearing the codes, take the vehicle for a test drive to ensure that the “Steering Assist Reduced” message doesn’t return.

Remember, these steps are only a guide and what has worked for me (I’ve got this message 3 times). Actual diagnostics and repair is always best performed by a professional to ensure the work is done correctly and safely.

When I first encountered this warning message, I found this video helpful:

How To Avoid Getting This Message In The Future

There are several preventative measures you can take to avoid this annoying “steering assist is reduced drive with care” warning message.

These are mainly regular maintenance procedures and while these steps can reduce the likelihood of issues, they cannot guarantee you’ll never see this warning, as some problems may arise from factors beyond regular maintenance.

  • 1. Regularly Check Coolant Levels and Quality: The coolant should be within the recommended level, and it should be clean without any discoloration or debris. Replace the coolant as per the manufacturer’s recommended interval or if its quality seems poor.
  • 2. Thermostat Maintenance: Ensure your thermostat is working properly. A faulty thermostat might cause an incorrect coolant temperature reading which may in turn trigger the “Steering Assist Reduced, Drive with Care” message. Regular inspection of the thermostat or its timely replacement according to the manufacturer’s schedule can prevent this issue.
  • 3. Maintain the Coolant Temperature Sensor: This sensor provides data to the Engine Control Module (ECM), which in turn communicates with the power steering system. If the sensor provides inaccurate data (often due to age or wear), it can lead to problems (which I mentioned earlier in this article). Regular inspection and timely replacement of the sensor can help avoid potential issues
  • 4. Regular Servicing of Your Vehicle: Regular servicing as per your vehicle’s maintenance schedule can help catch issues early before they turn into bigger problems. This includes checking the various modules and their communication lines for any errors or fault codes.
  • 5. Maintaining Battery Health: A weak battery can sometimes cause issues with the different modules in your vehicle. Regular checkups of your vehicle’s battery health can prevent such issues.

From every issue I’ve had with my cars I’ve learnt the hard way that regular maintenance is not only the best way to avoid the “Steering Assist Reduced” warning message, but also for averting most issues related to GMCs and vehicles in general.


Though this warning message may seem daunting at first, proper diagnosis, timely intervention, and routine maintenance can alleviate this issue.

It’s crucial to note that although we have provided a general guide for understanding this problem, repairs should always be carried out by professionals to ensure safety and effectiveness.