27E4 Brake Vacuum Sensor GOOD NEWS

So,

I got the dreaded 27E4 after a recent brake flush. Though I suspect that fluid had been on the sensor awhile, and the flush finally pushed the sensor to the limit.

I realize you need to just get the OEM part 34302283605 and remove the sensor, and replace the sensor on the car.

HOWEVER, there was a lot of discussion around part 13628657300 which is labeled as a diff pressure sensor, but all the numbers on the sensor match exactly with the sensor on oem part 34302283605.

Well I bought a used diff pressure sensor (13628657300) off a 2014 x2 I believe with about 20k miles, and it seems to be working!

I'm not surprised, I mean its a sensor, it does the same thing no matter where it is in the car, the ECU just determines is range/function based on where its plugged in be it diff, abs, intake etc.

I'll probably replace with a brand new 13628657300 when I muster up to doing that tedious task again. But I think its safe to say its a cross compatible part, saving you about $130!

Also replaced the this sensor, a few weeks ago. Totally fixed my limp mode, vac pump on all the time, and 27E4 fault code.

Wish I had known could've bought just the sensor; would've saved $120. I'll keep that in mind for next time, thanks!

chutak wrote

Also replaced the this sensor, a few weeks ago. Totally fixed my limp mode, vac pump on all the time, and 27E4 fault code.

Wish I had known could've bought just the sensor; would've saved $120. I'll keep that in mind for next time, thanks!

Well it's not a major savings but helps!

Have you noticed your abs pump cycling less since replacing? I don't think I've heard mine on the past few startups

Yes, I mentioned vac pump but maybe I meant abs pump. Whatever buzzing sound that comes from the footwell or driver side fender. It was on a lot before replacing the sensor, now I never hear it.

chutak wrote

Yes, I mentioned vac pump but maybe I meant abs pump. Whatever buzzing sound that comes from the footwell or driver side fender. It was on a lot before replacing the sensor, now I never hear it.

Okay thats good to hear. It would kick on every morning when I'd start the car over the past year or so. After the flush, it started happening multiple times while driving. Now I don't hear it at all either.

Adding pics of the new sensor (diff pressure sensor). vs the old sensor I took out.

13628657300 pops up as an intake manifold pressure sensor. Its pretty cheap too, like $50.

Glad I found this thread! I flushed the brakes last week and . . . got the warning lights/limp mode today!

Tonight I pulled the old sensor--it had a bit of brake fluid on one of the mounting ears, but nowhere else. I don't know it it is good or not, but it's out! When I pulled it out I heard a large "pop" and an inrush of air as it entered what I presume was the vacuum system. I have a new sensor on order and will install it and hope for the best.

WAKman wrote

Tonight I pulled the old sensor--it had a bit of brake fluid on one of the mounting ears, but nowhere else. I don't know it it is good or not, but it's out! When I pulled it out I heard a large "pop" and an inrush of air as it entered what I presume was the vacuum system. I have a new sensor on order and will install it and hope for the best.

It was probably enough to ruin it. As you heard the system is under vacuum. My guess is fluid gets pulled from the vacuum pressure then forced up into the senor ruining it.

My fluid was dusty coated all over the sensor. I think it got spilled on when BMW did it for the last owner. Then the pressure changes from my recent flush caused the sensor to be pushed over the limit

aututto wrote

It was probably enough to ruin it. As you heard the system is under vacuum. My guess is fluid gets pulled from the vacuum pressure then forced up into the senor ruining it.

My fluid was dusty coated all over the sensor. I think it got spilled on when BMW did it for the last owner. Then the pressure changes from my recent flush caused the sensor to be pushed over the limit

I plan on doing this replacement soon, I was wondering if you recall what type and size bolt it's attached with. Thanks.

RedCardinal wrote

aututto wrote

It was probably enough to ruin it. As you heard the system is under vacuum. My guess is fluid gets pulled from the vacuum pressure then forced up into the senor ruining it.

My fluid was dusty coated all over the sensor. I think it got spilled on when BMW did it for the last owner. Then the pressure changes from my recent flush caused the sensor to be pushed over the limit

I plan on doing this replacement soon, I was wondering if you recall what type and size bolt it's attached with. Thanks.

Read through the attached thread. I have done a couple. You will need a ratchet, long extension (preferably a wobble extension) and torx bit. Can't recall the size. A very long screwdriver just to push the sensor over a little for access and an extendable magnet helps as well in case you drop a torx screw into the abyss. You do NOT need to remove the master cylinder reservoir. If you unbolt the ABS block you can push it over for more room. Everything else you will find here-

https://www.m3post.com/forums/showthread.php?t=1338052

It is not nearly as bad as it seems, but requires finesse.

Dpc2u wrote

Read through the attached thread. I have done a couple. You will need a ratchet, long extension (preferably a wobble extension) and torx bit. Can't recall the size. A very long screwdriver just to push the sensor over a little for access and an extendable magnet helps as well in case you drop a torx screw into the abyss. You do NOT need to remove the master cylinder reservoir. If you unbolt the ABS block you can push it over for more room. Everything else you will find here-

https://www.m3post.com/forums/showthread.php?t=1338052

It is not nearly as bad as it seems, but requires finesse.

I read the torx is a T15. I look forward to losing some arm skin tomorrow ;-)

Thanks!

My car has thrown this code twice in the last few weeks. Once after about an hour drive and again a couple weeks later, after only about 10 minutes. There doesn’t seem to be any evidence of spilled brake fluid on the sensor or connector. When it does go into limp mode, I just pull over and restart the car. It doesn’t happen again for days or weeks. With an intermittent code like that, is it likely the seal on the sensor periodically leaking and just replace the sensor or do you guys think it could be pointing to something else? Thank you.

knous81 wrote

My car has thrown this code twice in the last few weeks. Once after about an hour drive and again a couple weeks later, after only about 10 minutes. There doesn’t seem to be any evidence of spilled brake fluid on the sensor or connector. When it does go into limp mode, I just pull over and restart the car. It doesn’t happen again for days or weeks. With an intermittent code like that, is it likely the seal on the sensor periodically leaking and just replace the sensor or do you guys think it could be pointing to something else? Thank you.

If the sensor have gone you should hear the vacuum pump buzz (left side engine bay), if not I'd assume its something else maybe the pump itself.

As a side note my pump buzz around for a bit more since I changed the fluid couple of years ago (and yes, over spilled...). Bought a cheap sensor after reading this post, never got worse so haven't got around to change it.

Cheers,
Mr Lazy

Helmsman wrote

If the sensor have gone you should hear the vacuum pump buzz (left side engine bay), if not I'd assume its something else maybe the pump itself.

As a side note my pump buzz around for a bit more since I changed the fluid couple of years ago (and yes, over spilled...). Bought a cheap sensor after reading this post, never got worse so haven't got around to change it.

Cheers,
Mr Lazy

Thanks. Yeah, I can hear the pump running. I would think if the sensor was bad, it would be more consistent. I’ve got one of the cheap ones on order and should be here tomorrow, I’ll swap it out and see what happens.

Problem solved, was a jacked oring on the sensor.

knous81 wrote

Problem solved, was a jacked oring on the sensor.

Nice find! And how many fingers did it cost to squeeze in and replace it..?

Helmsman wrote

Nice find! And how many fingers did it cost to squeeze in and replace it..?

Lol! None, extensions, long pliers, ect… Never put any hands in the abyss.

That blue o-ring on the sensor can get ripped during install or even removal. It might not be the o-ring itself but perhaps the sensor itself causing the code.

I replaced my sensor in 2022 and then in 2023 the sensor and vacuum lines as part of a master cylinder, brake booster, and reservoir refresh. The one year old sensor's o-ring looked about that bad but I didn't have codes.

This thread was very helpful for me. I started noticing the pump ran nonstop the moment I picked my car up from a brake job approx. one month ago. Then, two weeks ago, the car went into limp mode, but the car didn't store any codes. I drove the car two more times, and it went into limp mode again the second drive, this time storing the 27E4 code.

I spoke with the shop, and their head mechanic told me there was no way the sensor could've gone bad and that something else must be the culprit. I asked him to check the sensor, and after some colorful back and forth, he finally relented and swapped out the sensor. The car has only been driven 50 miles since the repair, but the pump has not come back on, except for 3-4 seconds upon startup.

Giving the shop the benefit of the doubt, I tried to pay for the replacement, but the shop's owner insisted on covering the cost, as it appeared they did let brake fluid drip onto the vacuum line, which trickled down to the sensor.

jmeenach wrote

Giving the shop the benefit of the doubt, I tried to pay for the replacement, but the shop's owner insisted on covering the cost, as it appeared they did let brake fluid drip onto the vacuum line, which trickled down to the sensor.

The way you like to be treated by the shop, good stuff!