[Fitz]

First off, I’m not providing a complete explanation – I’m seeking one! I titled the thead this way for future information seekers.

Can anyone provide (or point to) a good overview of Limp Home mode in our E39 M5s? Stuff like: What kinds of things cause it? What does it feel like when it occurs? How does it get reset? All I really know is that it’s a protective feature and it causes the SES to come on – and I couldn’t find much detail by searching previous threads.

Reason for asking is that I was at the track this past weekend and saw two Minis go into Limp Home mode. I myself suffered a power loss at high RPMs, but think it may just be the fuel filter. I don’t think what I experienced was Limp Home mode. (Sort of like getting sympathetic symptoms when a loved one gets sick ?!) Anyway, I’m not seeking help with my own diagnosis, just looking to learn more about Limp Home.

Thanks in advance for any help.

 

[Ladykats]

Limp home mode is not just on our M5's but applies to most OBDII model vehicles. Limp home mode generally sets the check engine light and the DME ( BMW ) or PCM simulates the valves of the failed sensor to get you home. This does not apply to all sensors. Some failure will cause a no start situtation that is out of control of the PCM. It is there to serve two purposes, one to allow you to get home or to a repair facility and second, to protect the engine. In some cases it will retard the drivability of the vehicle. The check engine like will go on and if it is flashing, it is letting you know that damage is being done to the catalytic converter. Hope this answers your question.

 

[Fitz]

That helps, Yes.
It sounds like there is a wide range of things that can occur, all lumped together under Limp Home mode. So you can't really know if you're in that mode, or just experiencing some engine difficulty, without reading the codes. Is this a correct statement?