My wife’s 2010 XC90 has been having gremlins lately. Right now it’s having a C111802 error that is showing as two messages, “anti-skid service required” and “brake assist service required”. It’s an “intermittent” error in the sense that the messages don’t always show when the car is in accessory or directly after starting, but they will show usually when the brake is compressed, or after it is compressed a few times.
I didn’t notice the second message and changed the clock spring because and OBD-II wasn’t pulling a code. After that didn’t work I was able to get the code pulled and then got the C111802 code. That code seems to always indicate a bad brake pedal position sensor. I bought one from AutoZone and replaced. When I pulled the original sensor off I did not find the O-ring that was on it. I assumed it fell in the engine. I installed the new sensor and it did not fix the error, and it was still “intermittent”. The AutoZone part did look to be old so I ordered another off Amazon. When I took the AutoZone part off I again did not find the O-ring. I made sure to take it off slowly, but it appears both O-rings were sucked into the break booster. The second brake pedal position sensor also did not solve my problem.
Other important info:
1. About a month an a half ago the passenger side CV axle blew up. It shredded the boot and I found two of the bearings on the road. This was a part that the shop put in from O-Reilly after an accident. When it blew my wife said the brakes went out. I tested the brakes when I got there and the pedal went straight to the floor. I pumped them and they came back. We have not had a problem with the brakes since then, but this problem cropped up barely a month later. I did have a transmission shop look at everything and they said there were no other problems, it was just a bad part.
2. I did the vacuum pump rebuild kit a couple of years ago.
3. It does not appear that the system is losing pressure. When I pull off the brake pedal pressure sensor it is still under vacuum, which is why the two O-rings were sucked in. I also do not hear any hissing, but my hearing is 44 year old good.
4. Last night I did a little more investigating on the booster just to see if I saw anything. I did not lose my O-ring this time, lol. I saw something that looked like a vacuum hose inside the brake booster just to the right of the opening for the sensor. I moved it slightly to see what it was, but not hard enough to dislodge anything.
5. Last night, when I put the sensor back in and turned the car back on the brakes were much stiffer than they’ve been. They were still responsive and the booster was working, but they had been much spongier before. Again, they were responsive before, but there was not much resistance from what I could ever remember. Now they are stiff.
Questions:
1. What should I try next?
2. I’m being told it is always the brake pedal position sensor or the wiring to it. Could it be anything else? And how do I check the wiring?
3. Are the two O-rings in my brake booster a problem? What do I do about that if they are?
4. What is the hose (or what looks like it) inside the brake booster?