Code 27E3 after Brake Fluid Swap

Just got this code and also have noticed in the mornings, before starting my car, that the brake pedal is stiff. I think this means there is a leak in the vacuum system?

27E3: Vacuum sensor, brake booster, plausibility

Sensor value deviates substantially from model value, with sensor value > Model value ensuring that ELUP activation threshold remains valid

What you should do if this comes back:
1. Check vacuum lines
2. Check 1-way check valves
3. Check brake booster

Happens all the time where the fluid leaks down past the reservoir and gets on the sensor. Will keep throwing the car into limp mode.

Replace the sensor, clean up the wires and reservoir and bleed the system. Hopefully that solves the issue.

This means you overfilled the fluid, and it has now dripped onto the sensor and killed it.

Buy a new censor, replace through the wheel liner, then you are all set.

http://www.m3post.com/forums/showpost.php?p=14464427&postcount=3

Thanks guys. Since the pedal is now stiff in the morning would you think there is also a leak as well?

I think the replacement sensor comes with some tubing as well so I'll probably start there and see if the pedal is still going stiff. Unless there are other tubes you would recommend I should order and replace while I am in there? http://www.realoem.com/bmw/enUS/showparts?id=KG93-USA---E92N-BMW-M3&diagId=34_1627

Leonardo629 wrote

This means you overfilled the fluid, and it has now dripped onto the sensor and killed it.

Buy a new censor, replace through the wheel liner, then you are all set.

http://www.m3post.com/forums/showpost.php?p=14464427&postcount=3

Wheel liner? Wouldn't have thought of that. Thanks for the tip.

Fluid overfilled and damaged the sensor.

The sensor is sold with the tubing it attaches to which sits right under the fluid reservoir. If any brake fluid gets on the sensor it needs to get replaced. Another symptom is that the vacuum pump it controls may start to run more often than it should. To change the whole part requires removing the brake fluid reservoir. With enough patience and the right flexible extensions, you can remove the sensor from the tubing and just replace it.

I have had the same problem also. Fluid was filled to the top from the factory and after the service filled to the top. I am thinking it should be filled more to he middle between full and low. Probably more so if brakes are used hard, like competition or spirited driving, to allow for expansion.

Why is everyone saying it's accessible from Wheel liner? On my E90 it appears the only way to access it is from the top after you remove the filters and cowl.





I threw the code this afternoon in some stop and go traffic. So I pulled the cowling apart to take a look at the sensor and it's completely dry. I'm going to have to look elsewhere for the problem. Is it possible to remove the brake booster without major disassembly or have to bleed the brakes to gain access to the sensor and tubing?

Well, I had this problem and I had to change the sensor, but it does not sell separately. Only with the hose together.

PN: 34302283605

Titan_br wrote

Well, I had this problem and I had to change the sensor, but it does not sell separately. Only with the hose together.

PN: 34302283605

And how did u go about Replacing sensor? Shit is tight in that area.

Hierlevelz wrote

And how did u go about Replacing sensor? Shit is tight in that area.

You have to take out everything..it is a hard work. In the end I changed the hose, since it came together with the sensor.

I know I'm reviving an old thread, but for anyone looking to replace the sensor, you do NOT need to remove the reservoir or unbolt the ABS unit or disconnect any lines or bleed the brakes. You can't get your hands in there so everything has to be done slowly and methodically with tools. Use a very long screwdriver or extension bar to move the vacuum tube with the sensor about an inch toward the front of the car. This will move the sensor into a position where the screws holding it can be accessed by another long extension with a 15 torx bit on the end. Unscrew the screws slowly until they are out of the threads but still sitting in the sensor mounting holes. Use a magnet or claw device to lift the screws out and bring to the surface. Now use any kind of tool with a hook/bend at the end (I used a paint can opener) grab the edge of the sensor (near the screw holes is best) and pull up to dislodge it from the tube. Now that it is free, use the wire which is still attached to the sensor to pull it up to the surface. Now you got your sensor out, unplug it, plug in the new one, and reverse the process to install the new one. It is a slow and tedious process getting the new sensor into place and getting the screws back in without dropping them into the abyss. But if you're patient and operate like a surgeon, this procedure can be done in about 30 minutes and there is no need to bleed the brakes or mess with brake fluid in any way.