Hello, we have a 2014 CX9 front wheel drive. It has around 200k miles and never given us an issue. We love it.

However, this week, it stopped wanting to stop. When you press the brake, a hissing sound can be hear from the area of the booster, and the brakes are hard and not wanting to stop, however it is not tripping any abs or warning lights of any kind.

Also some times it works just fine. It is a hit and miss issue. Could it be a faulty hose that leads to the booster?

It may work just fine the first 3 times you stop. Then stop working and then start again. Or just the opposite.

I am quite mechanically inclined so I can fix if I know the problem. Searching the forums I have seen people saw it is an ABS module or it is the booster., but they all have codes of some time. I am on a tight budget, and cannot afford to have a dealership diagnosis it.

Where should I start?

 

There would not necessarily be any cautionary light or DTC.
A vacuum gauge connected to the any hose that is past the throttle body can confirm a vacuum leak which would be your booster hose. Or you can just go look at that hose and feel around while the engine is running and an assistant is pumping the brake pedal.

 

Is the brake warning light activated by anything other than the fluid level in the reservoir or the parking brake on? If those are OK then there won't be a warning light.

 

Your model CX-9 is well known for brake booster failures.