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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > 2012-2019 BMW 3 and 4-Series Forums > General F30 Sedan / F32 Coupe / F36 Gran Coupe Forum > What exactly is limp mode?
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      01-13-2014, 05:55 AM   #1
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Question Please Read The Full Post Carefully

Well, we all know the purpose of limp mode - to get you and the car to safety whilst severely limiting power to protect the engine/transmission from further damage. Excellent feature.

But how exactly does it do this? From what I've heard and understand, the turbo(s) is shutdown and the Valvetronic hardware is deactivated. We actually have traditional butterfly throttle valves but under normal operating conditions, your throttle inputs actually control the Valvetronic hardware so the butterfly valve is rendered superfluous, except in limp mode where I believe that is now operational instead. However, it is still completely electronically controlled by the ECU as there is no cable linkage (which is obviously the case for the majority of modern cars) so you can boot it but it'll barely open under limp conditions.

How else does it protect itself? Just a curiosity!

Thankfully, I've never experienced limp mode in any BMW.
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      01-13-2014, 09:53 AM   #2
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It sucks...you basically have 25% power(all the times Ive had it I am able to rev above 3k but with barely any power), the fan then kicks in because it is tricked that something is overheating. Once you turn the car off and on its all good again
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      01-13-2014, 10:30 AM   #3
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Well, it has never happened to me, but...Oh, the BMW limp mode? It's what btbossman described.
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      01-13-2014, 10:43 AM   #4
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Quote:
Originally Posted by OC40 View Post
Well, it has never happened to me, but...Oh, the BMW limp mode? It's what btbossman described.
Yep, got what Limp Mode is in the OP - I'm just curious as to HOW the engine restricts itself - i.e. what it shuts down, what it changes, etc...
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      01-13-2014, 05:31 PM   #5
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Quote:
Originally Posted by SomeRandomer123 View Post
Yep, got what Limp Mode is in the OP - I'm just curious as to HOW the engine restricts itself - i.e. what it shuts down, what it changes, etc...
Its clearly a software issue. You do something that tricks the system, and boom, "limp mode".

The weird thing is Ive had 7...I can count at least 3 different ways that triggered it

-switching from comfort to sport+(had that twice)
-simply down shifting in MDM (3 times)
-Spirited driving into lawful driving (twice) One of those was the weirdest thing, I was running the car pretty hard on some hills, then come to a stop, and boom, Im limp.(it was also my first) thank god I had read the thread and new what to do, because I was far from home.
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      01-13-2014, 05:46 PM   #6
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My dad's x5 got the exact same thing as limp mode. The repair shop diagnosed the car and it was a transfer case problem.
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      01-13-2014, 06:33 PM   #7
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Folks are going off track here. He's not referring to the 335i M Sport fan issue. He's referring to "limp mode" in general. Any of a multitude of issues can trigger a limp mode event. I don't know the exact specifics of how the F30 responds.
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      01-13-2014, 08:16 PM   #8
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Quote:
Originally Posted by BavarianFanatic
Folks are going off track here. He's not referring to the 335i M Sport fan issue. He's referring to "limp mode" in general. Any of a multitude of issues can trigger a limp mode event. I don't know the exact specifics of how the F30 responds.
+1, guys read the fecking OP!! I know what limp mode is, I know what could trigger limp mode, I know what the purpose of limp mode is, etc...

I'm not referring to any issue specifically that triggers limp mode!!

I want to get technical. I stress again - HOW does limp mode fully work? Please read my OP about the turbo, Valvetronic hardware and butterfly valve - I only (think I) know some of the process and want to learn more.

Please carefully read and don't just leap to the last line of me thankfully never experiencing limp mode in a BMW.

SAME GOES FOR THIS BLOODY POST!!!
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      01-13-2014, 08:17 PM   #9
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Quote:
Originally Posted by Dan_335i
My dad's x5 got the exact same thing as limp mode. The repair shop diagnosed the car and it was a transfer case problem.
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      01-13-2014, 08:18 PM   #10
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Quote:
Originally Posted by btbossman
Quote:
Originally Posted by SomeRandomer123 View Post
Yep, got what Limp Mode is in the OP - I'm just curious as to HOW the engine restricts itself - i.e. what it shuts down, what it changes, etc...
Its clearly a software issue. You do something that tricks the system, and boom, "limp mode".

The weird thing is Ive had 7...I can count at least 3 different ways that triggered it

-switching from comfort to sport+(had that twice)
-simply down shifting in MDM (3 times)
-Spirited driving into lawful driving (twice) One of those was the weirdest thing, I was running the car pretty hard on some hills, then come to a stop, and boom, Im limp.(it was also my first) thank god I had read the thread and new what to do, because I was far from home.
Though I appreciate your post,
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