What would cause the brake assist light to come on?

The brake assist is basically the power brake system. On this vehicle, it is a vacuum brake assist system. The light can indicate a vacuum leak, low vacuum pressure (it may have a vacuum sensor), and so on.

Try this. Open the hood and have a helper start the vehicle. Behind the brake master cylinder is the vacuum brake booster. Listen to hear if you notice any hissing sounds. Also, when the engine is turned off, listen if there is noise.

Next, the vehicle is somewhat newer. What you can do is scan the can-bus system to see if there are specific diagnostic codes. CAN stands for controller area network. Basically, all the computers/modules are tied together via this system. If you scan the system, it should show codes regardless of the module they are stored in. Here is a video showing how it's done:

https://youtu.be/InIlnsjOVFA

If you look at the attachments below, they provide the diagnostics for locating a problem with this system. Take a look through them and let me know if you feel comfortable doing them.

I do have one last question. Have you noticed the brake pedal being stiff or difficult to depress?

Let me know.

Take care,

Joe

See pics below.

I'm getting this info. for a friend , he has the car problem . Thank you

My friend took his car and had it scanned and they said it was the back drivers side brake sensor. He has installed it , I'll let you know his results in a few days. thanks for your answer. Your answers are appreciated so much and they are very helpful.

Hi,

You are very welcome. If possible, let me know how things turn out for your friend.

Please feel free to come back anytime in the future if you have questions. You are always welcome here.

Take care,

Joe

I will, thanks.

He took his Malibu back to them because the sensor didn't fix it and they said it had to be the bearing. so he's replacing that bearing.

Hi,

Thanks for the update. It must have been an ABS issue.
Again, please feel free to come back anytime in the future.

Take care,

Joe