My car is going nuts
 

I’ve had similiar trouble on the 08 4.8i before and checked the wiring harness, tested another thorttle body, chnaged the gas paddle and it ended up being the battery. However now the battery is holding charge fine. Here are the nuts symptoms: Car started going into limp mode but no errors, simply i mashed the paddle and the car would not accelerate, had to turn it on/off and it would be a while till the car went into limp mode, still no errors. This sometiems did and sometimes didn’t happen. These days it went in limp mode and i got the 4x4 malfunction and various warnings, cruise control malfunction etc. Today the really nuts behavior re-accured: the car started bucking forward, without me giving it gas, it stalled, the rpms kept going up and down and i could barely drive it. Left it sit and the car started back up no issues, last time i checked here are the codes: 2CF8 throttle potentiometer, 2CF9 throttle potentiometer 2, 2CFA throttle potentiometer 3, 2D32 differential pressure sensor plausibilty error. These come up when the engine malfunction light comes up. It probably had more codes but they got erased as the car has been from shop to shop and they’ve got no clues including the BMW dealer. They’re advising i try changing the throttle body. Any ideas ?


Here is a video of it going into limp mode without any warning, and after a turn off/on: https://youtu.be/DLWsDDoCulg

Just a guess but it might be the DME unit (the brains of the engine--controls every calculation in the engine). I had mine replaced luckily in April 2016 (there is an 8 year warranty on them from BMW). The failure rate on those is really, really low though--like 1 car in 300 they go bad.

Thanks for the suggestion. I would not doubt that this isn't the 1 in the 300, i will have to check. Do you know where the DME is located? Why did you have yours replaced?

I'm not sure where it's located. My car shut down on the freeway and threw up a bunch of codes--that's all I remember specifically.

Same issues in the past changed a used throttle body on eBay 20$ gas pedal and throttle body harness easy check xoutpost for diy

Really? You had THE SAME THREE CODES?????

1 in 300? That's a recall

Try one in 10,000

id be hard pressed to suggest he chase after DME issues .

OP, how do you know the battery is good? 'Holding a charge' is not a great test. If the car did the same things before, and that was a bad battery, it would seem easy to rule out a battery. Like 200 euros easy...

Just changed the throttle body again yesterday, same issue however it did not go erratic, but that happens only sometimes after going into limp mode and the car kept throwing the same errors. The harness they're calming is not the issue, but i'll have to check that again.

Well the first time the battery voltage would drop to 9 volts when starting the car. Why i'm sort of ruling the battery out is because it's been changed about a month ago and the issue was gone after that. I find that very strange that the same errors went away for over an entire month, and i drove the car everyday. :dunno:

9V sounds a bit low but don't forget your starter motor draws *a lot* of current, which will lead to a temporary voltage drop.

I didn't say it was the DME--it was a suggestion as he said so many codes came up he didn't have them all written down. The 1 in 300 DMEs is all BMW model DMEs not just X5--per the dealer that had to replace it.

Today while i asked to re-check the throttle body harmess, as i want to order one but it will take a while for it to ship here, i turned the car on without the covers or the air filters and the cars rpms were jumpy, there was a hiss sound that was happening when the rpms went higher and stopped as they dropped to normal levels, then they would drop to slightly below 500 and back up.(this happens always you can see the rpms often jumping) Monday they’ll check, i think that might be causing the issue. Considering that the car has been checked by two dealerships and multiple shops and none noticed..

Now the car drops to around 11V with the new battery.

Do the throttle body harnes its like 24$ on eBay u just cut and splice the new one I'm sure that will take care of it

I'm looking for one closer to me otherwise i'll have to go with the eBay options ,$50 for the shipping, though it will take around a month for it to get here. :tapping:

An update: I got a throttle harness, however i did not need to install it yet. I noticed that the car generally felt bogged down and sluggish after checking a few things i noticed that the car was running hot and the temps were never dropping, turns out the thermostat wasn't opening at all or barely opening! I drove like this for at least two weeks that i know, during that period the transmission went and i've started having all sorts of troubles, anyone know what else may have been damaged that i may need to check and are you aware at what temp does the hot temperature warning come on, as i never saw that after my auxiliary fan and radiator broke, anyway i might open another thread to ask these. The issues did not come back until now.

These are the codes the car kept throwing when the issue occurred, when the engine malfunction light appeared the last two came up.
2D32 - Differential Pressure Sensore
2CF8 - Throttle potentiometer
2CFA - Throttle Potentiometer 2
2D13 - Air Mass sensor, rationality
2F03 - Intake air temperature signal

X2. Had similar problems with my car. My dash was lit up like a Christmas tree, limp mode, the works. Replacing the harness fixed my car. If you plug these OBDII codes into Identifix, it will point to a TSB about the harness.

Keep in mind that the "harness" in question is merely a plug connector with about 18" of wires coming out, the first 12" or so covered in black plastic sheathing. I got mine at my local dealer, they had them in stock, (tells you something right there). It was not expensive.