Engine limp mode randomly

[phantome46]

My E92 M3 has been behaving very well and the last time I drove it was a joy. Recently the battery went very low - yellow battery light on dash. I put the car on a CTEK and recharged the battery/restored it fully. now its holding about 12.9V

Anyways when you now start the car immediately you get the engine check light and reduced power mode comes on. The car will not rev and even the idle is very lumpy and sometimes nearly stalls.

I have put the code reader on it - ISTA+ and got the following codes

2794 - DME brake booster vacuum pump signal
27E4 - DME brake booster vacuum pump plausibility

I cleaned down the faults and then closed car, 5 mins passed and then restarted and they come straight back.

From what I have read some say its vacuum line and sensor by the brake servo.

Can anyone help with this or have experience?

Thanks

[Shiza]

It's common. You need this. If it helps you can just remove the sensor from the new vacuum line and throw it in the old one.

https://www.fcpeuro.com/products/bmw...vD_BwE#fitment

[phantome46]

Originally Posted by Shiza

It's common. You need this. If it helps you can just remove the sensor from the new vacuum line and throw it in the old one.

https://www.fcpeuro.com/products/bmw...vD_BwE#fitment

Thanks I will look into this now!

[Adriano917]

Same thing happened to me but it ended up being the pump. You can just buy the sensor and not the entire assembly if you want to start there. https://www.fcpeuro.com/products/bmw...or-13628617097