Brake booster vacuum

Hi guys!

I’m in need of some help!
So my car started to go in limp mode because of the code 27e4 which is for the brake vacuum sensor. I changed the sensor, fuse #67. I don’t had fuse #69. The car is doing the same and as I checked other posts of it for most of the people their car is going into limp mode when they’re on throttle. Mine is not like that my car going into limp mode on idle and it’s going into limp mode when I press on the brakes.

So the question is does somebody had issue like that and if yes what was the solution for it? Do I need to buy a new pump or somehow check the pipes?

Thanks for reply’s!

When you say sensor, you replaced the vacuum sensor under the master cylinder, yea?

I had the same issue and replacing the sensor (I did lines as well as it came as a whole assembly) fixed my issue.

If sensor is replaced I’d start looking at your pump. What’s your vacuum pump doing? Do you hear it running after you push on the brake pedal? Does it keep running or does it stop?

Do you have ISTA or INPA? Iirc there’s a test you can run / monitor you can use to help you determine what’s going on.

chicagob5 wrote

When you say sensor, you replaced the vacuum sensor under the master cylinder, yea?

I had the same issue and replacing the sensor (I did lines as well as it came as a whole assembly) fixed my issue.

If sensor is replaced I’d start looking at your pump. What’s your vacuum pump doing? Do you hear it running after you push on the brake pedal? Does it keep running or does it stop?

Do you have ISTA or INPA? Iirc there’s a test you can run / monitor you can use to help you determine what’s going on.

Yes I mean replaced the vacuum sensor.

I can hear my vacuum pump is working after I press the brake and also on idle sometimes also heat It working with normal sound like before when I don’t had the issue.
When I hear it working longer times the car is going into limp mode, so if I press and hold the brake it will go into limp mode after around 5-10sec.

That’s a good thing to know I need to buy a laptop with bigger storage to have the Ista installed, but if inpa also has the test I will work on it somehow.

Thanks for your reply!

If you have INPA, you should be able to find the live data for the brake vacuum or “Bremsunterdruck” to get an idea of what the sensor is seeing.

Good luck! 🍀

chicagob5 wrote

If you have INPA, you should be able to find the live data for the brake vacuum or “Bremsunterdruck” to get an idea of what the sensor is seeing.

Good luck! 🍀

Thanks for it, I will check tonight!

chicagob5 wrote

If you have INPA, you should be able to find the live data for the brake vacuum or “Bremsunterdruck” to get an idea of what the sensor is seeing.

Good luck! 🍀

Tried to check, but I can’t seem to find it in inpa.

I got ista also but I cannot connect to the car, from last night I’m trying everything with it but still can’t do it.

Got it figured out!

With ista I was able to check the vacuum level and with stopped engine I saw that there is a vacuum leak in the system. So next step was to locate it.
There is a vacuum valve near the idle control valve and I found that in pieces. But since it’s only available with the hose I ordered a vacuum valve from Amazon and fixed it with some clamps.

Car runs fine after it!

rfalusi wrote

Got it figured out!

With ista I was able to check the vacuum level and with stopped engine I saw that there is a vacuum leak in the system. So next step was to locate it.
There is a vacuum valve near the idle control valve and I found that in pieces. But since it’s only available with the hose I ordered a vacuum valve from Amazon and fixed it with some clamps.

Car runs fine after it!

This is a great find. Thanks for posting. No wonder the vacuum pump was running so much. Well done.

nice find.
Was your car going into limp mode almost immediately? or only once it was warmed up?

I'm trying to diagnose a 27E4 fault on mine - it failed after a 30 minute drive and the next time I ran it and left it idling on driveway, it dropped to limp mode and code 27E4 only after10 mins+. once the car was fully warm.