Sienna Brake Booster Pressure Sensor Failure

I also have a Sienna, and what you describe sounds awfully familiar. I had similar symptoms – felt like I was trying to stop Fred Flintstone’s car with my feet. Was your brake pedal feeling unusually stiff or going all the way to the floor?

The brake pedal feels normal, but the braking performance is definitely reduced. It is concerning. Did your issue also trigger a sensor error?

Yes, the sensor error was the key. Think of it like a faulty smoke detector, triggering for no real reason, but definitely a problem. In my case, it was the brake booster pressure sensor, likely damaged during a brake bleed. Given your symptoms and the sensor error, I strongly suggest taking it to a workshop to check the brake system.

Thank you for your guidance. It turned out to be a faulty sensor, almost certainly due to incorrect bleeding as suspected. The replacement cost 90€. I appreciate your help in diagnosing this.