4Runner Brake Booster Pressure Sensor Error

This sounds like an issue I had with my old Saab 9-3. Same symptoms: error message, weak brakes, and a code. It ended up being the brake booster vacuum line. Before replacing the booster, check all the hoses and connections. Could be a simple leak causing the pressure issue. Did the issue start right after the brake service, or was there a delay?

Thanks! The issue appeared a few days after the brake service, so I didn't immediately connect the two. Where was the vacuum leak on your Saab? Was it obvious, or did you need a smoke tester? I will take a closer look at the hoses and connections, but I'm assuming that the sensor itself is faulty.

On my Saab, the leak was a small crack in the hose right where it connected to the booster. It wasn’t super obvious, but once I wiggled the hose, I could hear hissing. Given yours started after a service, take it back to the shop and let them look. Could save you a headache, and they're probably responsible if it's related to their work.

You were right! It was indeed caused by air introduced into the hydraulic brake system during that poorly executed brake bleeding job! I went to a proper workshop, had the system professionally bled and the brake booster pressure sensor replaced. The error is gone, and the brakes are back to normal, all for around 90€ Thanks for pointing me in the right direction!