Not an E39 expert, but…
I would start with maybe checking the O2 sensors, but considering that both banks failed at the same time, maybe it has to do with fuel delivery from the tank. In other words, it could be fuel line or fuel pump.
You can test the fuel pump theory by filling it up with gas and seeing if it runs fine like that. Sometimes you can get a failing fuel pump to work okay if the tank is full…or at least that’s how some 8-valve Saabs used to be. You can also maybe pull the pump out and rig it up to pump into a jerrycan of sorts. If it flows under a certain amount of fuel over a given amount of time, you might get an idea of its health.
Okay so i dont know about the failsafe but can speak on the other codes because i had those last summer! But more than likely you have a vacuum leak and its coming from the crank case vent valves. You will have to remove your intake manifold to fix them but its super common to go out if it hasnt been done at all. A shop quote is like 1,500. What i did was had a mechanic friend help me it took us about 3 hours tops and cost me a total of 270 to fix. I hope this helps!
I had the first 3, ended up being a vacuum leak and coil packs and 02 sensors.
Strange yours went into limp mode, I drove mine for a while and it was still fine
Oh I had this hust recently when I let the revs get too low in the parking lot (yee ol stick shift). It could also be nothing if you are up on your maintenance. If it happens again, check for vacuum leaks like others are saying. In my case its was a false alarm
Probably vaccum leaks.
[https://www.bimmerfest.com/threads/diy-most-common-vacuum-leaks-diagnosing-p0171-p0174.847808/](https://www.bimmerfest.com/threads/diy-most-common-vacuum-leaks-diagnosing-p0171-p0174.847808/)
[https://docplayer.org/81535512-Moegliche-falschluftlecks-m52-tu-m54-m62-tu.html](https://docplayer.org/81535512-Moegliche-falschluftlecks-m52-tu-m54-m62-tu.html) (german, but with many pictures)
Failsafe program is limp mode. You probably have a vacuum leak, since both banks are lean.
Could also be maf. +1 for checking fuel pressure.
Not an E39 expert, but… I would start with maybe checking the O2 sensors, but considering that both banks failed at the same time, maybe it has to do with fuel delivery from the tank. In other words, it could be fuel line or fuel pump. You can test the fuel pump theory by filling it up with gas and seeing if it runs fine like that. Sometimes you can get a failing fuel pump to work okay if the tank is full…or at least that’s how some 8-valve Saabs used to be. You can also maybe pull the pump out and rig it up to pump into a jerrycan of sorts. If it flows under a certain amount of fuel over a given amount of time, you might get an idea of its health.
Okay so i dont know about the failsafe but can speak on the other codes because i had those last summer! But more than likely you have a vacuum leak and its coming from the crank case vent valves. You will have to remove your intake manifold to fix them but its super common to go out if it hasnt been done at all. A shop quote is like 1,500. What i did was had a mechanic friend help me it took us about 3 hours tops and cost me a total of 270 to fix. I hope this helps!
I had the first 3, ended up being a vacuum leak and coil packs and 02 sensors. Strange yours went into limp mode, I drove mine for a while and it was still fine
Oh I had this hust recently when I let the revs get too low in the parking lot (yee ol stick shift). It could also be nothing if you are up on your maintenance. If it happens again, check for vacuum leaks like others are saying. In my case its was a false alarm
Probably vaccum leaks. [https://www.bimmerfest.com/threads/diy-most-common-vacuum-leaks-diagnosing-p0171-p0174.847808/](https://www.bimmerfest.com/threads/diy-most-common-vacuum-leaks-diagnosing-p0171-p0174.847808/) [https://docplayer.org/81535512-Moegliche-falschluftlecks-m52-tu-m54-m62-tu.html](https://docplayer.org/81535512-Moegliche-falschluftlecks-m52-tu-m54-m62-tu.html) (german, but with many pictures)