SMG yellow cog light, unable to start car

[sapote]

So I know this topic has been beaten to death over and over but it would be nice to get some fresh information. Today I was driving and all of a sudden my car shifted from 2nd to neutral, then it shut off on me.

I know problem has been solved.
Q: when did it shift to neutral and then shut off the engine -- while still moving or at stop? I would think it does this at complete stop.

[erickhoyos]

I know problem has been solved.
Q: when did it shift to neutral and then shut off the engine -- while still moving or at stop? I would think it does this at complete stop.

While still moving. I was turning left when the yellow cog light came on, followed by the transmission shifting into neutral and then shutting off. Pretty scary if it would have happened on the highway

[sapote]

While still moving. I was turning left when the yellow cog light came on, followed by the transmission shifting into neutral and then shutting off. Pretty scary if it would have happened on the highway

The DME and SMG controllers not suppose to do this. It should only shift to neutral at a safe driving condition. Absolute not shut off engine while moving. It could be that suddenly in neutral the rpm dropped too low and stalled with ignition still ON. Was your foot on gas pedal when it shut off or throttle was closed?

[erickhoyos]

The DME and SMG controllers not suppose to do this. It should only shift to neutral at a safe driving condition. Absolute not shut off engine while moving. It could be that suddenly in neutral the rpm dropped too low and stalled with ignition still ON. Was your foot on gas pedal when it shut off or throttle was closed?

When it shut off on me throttle was closed because I wasn’t aware that the car went into neutral and rpms rose suddenly so I let my foot off the pedal to try and engage gear but it shut off. It was as if I turned the key to the off position, it was very sudden. I was going probably 20 mph, rpm was pretty stable when it went into neutral.

[Anativid]

First of all Hi and thanks for the add I just joined a week ago. A couple of years ago driving to work my 2004 M3 SMG went into "N" sitting at a light, no warnings , no previous slow shifting or erratic shifting, never had a problem starting like I have read some do. I heard a Ding when I looked at the Dash the "N" indicator wash flashing. I moved the shifter to Neutral the "N" quit flashing then back to gear and it started flashing again. I figured I'd turn the car off then back on....well when I did that the car didn't crank over anymore. I let it sit for 2 years because I was afraid it was the SMG pump and I didn't want to spend the money to fix it. I had just spent 4500 at the dealership for a rear main seal leak and some other little stuff. Anyway, last week I decided to take a look at it so I ordered a foxwell scanner with the BMW program. After learning how to use it about half a day or so, I tested the pump and it showed good pressure. I read the codes and had a 3B actuation, clutch dynamic code. I didn't know what it meant and after hours of searching I decided to tell the car I replaced the gear position sensor. The system then shifted through all the gears and indicated on the dash each gear. Doing this I ruled out the GPS sensor and also the Gear actuators that do the shifting of the gears. I decided it was the slave cylinder although mine didn't leak fluid like I have read they normally do. I changed the slave cylinder day before yesterday and used my foxwell to blend the system. Everything checked out, the SMG cog light cleared and the car started right away.
along my troubleshooting journey I noticed my gear indicator on my scanner showed "0" in neutral the dash showed "N" when I put it in gear it showed a flashing "8" dash showed flashing "N". I never did find out what this meant but I wanted to put this in hear in case someone searched for it. If someone knows please explain. Also in my scanner the clutch showed it to be "closed" status and I assumed that meant engaged. Again if someone can confirm please do. I also saw a message that my starter was blocked due to PN. I hope this information helps someone else because it took me a few days to build up 95% confidence it would be the slave cylinder.

[sapote]

A couple of years ago driving to work my 2004 M3 SMG went into "N" sitting at a light, no warnings

The system should not riding on the clutch while stopping a long period at the light -- bad for crank thrust bearing and clutch TOB. It should shift to N after some times and not moving.

when I put it in gear it showed a flashing "8" dash showed flashing "N". I never did find out what this meant

If a door or hood opened then the SMG computer will not shift and it flashes the warning.