[Mars328]

Hello Everyone, new to the forum (posting).

I hope that there is someone that can help.

i drive a2013 (2012 build) F30 328i Luxury line, and about 3 weeks ago whilst driving on the highway( freeway) it suddenly changed down 2 gears (ref counter picks up to about 5000 RPM) and then changes back to 8th gear.

i am not accelerating at all, it randomly changes about 2 gears down and back to normal again. (attached video).

i also sometimes get a Driveterrain error but it either clears within a minute or if i restart the error goes away.

I went to have the vehicle cheked and no errors came up at all.

i hope that there is someone that have experienced this that can point me into a direction please.

vehicle details : 2013 BMW F30 328i Luxury line
205 000km full service history at dealership.

[ATTACH]undefined[/ATTACH]

[NxTH]

It is impossible for errors to not show up after having a drivetrain malfunction unless the codes were cleared manually. The reader which was used was probably not able to read BMW specific codes.

Either

- Bring it to a shop where they can properly read the codes,
- Get a reader that can read BMW specific codes, or
- Get an OBD2 adapter and the Bimmerlink app.

Are you sure you didn't switch between Sport and Comfort or pushed the shifter to the left?

[Mars328]

Thanks for the feedback.

The person I did take the car to did a diagnostic and full reset and he is an bmw mechanic running his own thing for years. Very reputable. Although I do agree that a dealership scan might be better aswell.

100% sure I didn't switch to any modes, as the button is on the Centre console
Next to the gear lever, and I'm 100% sure that I didn't tap the gear select on the left or right side of the steering wheel.

I do however have a smaal issue ( picked up today). The exhaust actuater is not opening the valve in the exhaust... My experience tells me that can cause an issue due to adjusting of the timing etc..

[Wires]

Do you have paddle shifters? Bumping the left one would force a downshift, and then it would resume to the proper driver gear later.

[Mars328]

yes i do , 100% sure i didn't bump anything as the downshifts are 3-4 gears -

I'd be driving at 120km/h @ 2000 RPM, the downshift happens and the revs go up to 5000rpm, for about 2 seconds and then shifts normally back to 8th gear

did a diagnostic again today after not driving the weekend -

came up with: 123004 wastegate activation: line disconnected
12204 bypass blow off valve, activation : disconnected

[pshovest]

Downshifting can happen if there is a momentary loss of power, even if the loss is not noticeable.
Unexpected downshifting turned out to be an intermittent crank sensor on my N52 E70.
After multiple scans providing no good clues, ISTA finally reported a code for the crank sensor.

[Mars328]

after scanning it again at he dealer, they came up with a thermostat housing to be replaced, and said they dont pick up anything, and i will need to have that fixed.

I replaced it , test drove it about 80km and everything was perfect. was ecstatic -
this morning drove again, issue is back, im inclined to beleive that it is the crank shaft sensor aswell, misfeeding information,

taking it back tomorrow to have it looked at..

thanks for the feedback thus far.

[NxTH]

Originally Posted by Mars328

after scanning it again at he dealer, they came up with a thermostat housing to be replaced, and said they dont pick up anything, and i will need to have that fixed.

I replaced it , test drove it about 80km and everything was perfect. was ecstatic -
this morning drove again, issue is back, im inclined to beleive that it is the crank shaft sensor aswell, misfeeding information,

taking it back tomorrow to have it looked at..

thanks for the feedback thus far.

Sounds like they don't know how (or they don't want to) to diagnose errors, and rather just jump to the last option in the diagnosis process which is to replace a part that the error vaguely refers to. Easy money. When diagnosing an error, you check all the steps one by one, the conditions, the service plan, the fault impact, the warning lights and service notes.

These all come with the error when scanned with a proper reader. You then check all possible wires, the voltage, conditions, or what have you that could relate to the issue, etc. with ISTA or manually by observing them and then you have an answer. If there is a wire that's cut, obviously the error will tell you the unit the wire goes to, even if the unit itself is fine. Hopefully they don't make you replace 10 parts just for the fun of it. You can observe this by inputting any error into https://bmwfault.codes/ and seeing what it tells you to check. Many shops are happy to jump straight into the last step, which is to replace whatever the error hints at, and to do it over and over again.