Start-stop bizzare issue

[jay.nana777]

hi all,

first of all i hate start-stop, so i knock if off along with pressing the start button most often. on the rare occasion that it doesn't happen, i have sometimes experienced this bizarre issue:

When i stop at a traffic light etc, the engine sometimes stops, as normal. later when i press the accelerator the engine starts, as expected. but sometimes as the engine starts the gear indicator changes from D to P and the engine just revs up!! (and a few annoying honks would follow )

this is either intermittent or only happens when the the engine had been in the stopped-state for perhaps 20 secs or so..

firstly, has anyone else faced this issue?

secondly, any suggestions?

thx
j

[Qsilver7]

Wow...never have experienced anything like that. Just to rule it out...it is not happening due to accidental pressing of the P button on the gear "joystick", right (like if you're resting your hand on the joystick)?

I have no recommendation other than perhaps this is one that your local BMW dealership should take a look at...hopefully it's not difficult to replicate so that they can actually see what happens.

Here's a link to the TIS that discusses the functions of MSA (engine auto start/stop). Read through it to see if anything jumps out at you in regards to what may be causing the issue. There's a list of causes under the heading SWITCH-OFF inhibiters near the bottom of the page: https://www.newtis.info/tisv2/a/en/f...ction/F7qErV2j

BTW, how old is your car's battery? Low voltage is one of the things listed under switch-off inhibiters.

[Opie55]

Originally Posted by jay.nana777

hi all,

first of all i hate start-stop, so i knock if off along with pressing the start button most often. on the rare occasion that it doesn't happen, i have sometimes experienced this bizarre issue:

When i stop at a traffic light etc, the engine sometimes stops, as normal. later when i press the accelerator the engine starts, as expected. but sometimes as the engine starts the gear indicator changes from D to P and the engine just revs up!! (and a few annoying honks would follow )

this is either intermittent or only happens when the the engine had been in the stopped-state for perhaps 20 secs or so..

firstly, has anyone else faced this issue?

secondly, any suggestions?

thx
j

That is odd. Never saw anything like that. I take it that on your car you have to turn start stop off each time? I think it was maybe starting in 2014 that it would stay off permanently unless you switch it back on. I forget I have it, so on the rare occasions that I have accidentally turned it on I think I have stalled.

[MARKPRIOR]

Jay get it coded off, i have mine set to last position. so if i turn it off it stays off forever until i turn back on

[jay.nana777]

Thanks Qsilver7, no chance I hit P (or anything else) by accident, I have gone to the level of observing how the D changes to P as the engine starts. That was a good read. all this time i thought this might be a software glitch (and is it?). reading through i wonder if its some fault with the Hydraulic impulse storage which seems to allow the engine to start whilst in D.

Opie55 you're correct, remembering the start-stop disable came in circa 2014. not available in mine unfortunately. mine's 2011.

MARKPRIOR i've tried to code this off too (more so because i hate start-stop) below are the codes i looked for, in FEB_BODY:
TCM_MSA_DEFAULT_OFF
TCM_MSA_MEMORY

is that correct?

But the FEM_BODY module is not available in my car. possibly cos its a 2011.


Is there a software reset procedure on these cars? worth a try if there is i think..