Another trans fail safe
 

I think I tried my best searching here but still didn't find luck.

So the 4.8is tranny has just been recently overhauled by an indy. Shifts buttery smooth I can tell you. Following day after driving 3-4 km, car wont start and the trans fail prog error appears on the dash with the trifecta lights on as well.
Checking with INPA, the trans control unit could not be accessed and at one point the engine ECU as well. When the engine ECU could be accessed, fault code says something about CAN bus signal not returned or something.

Leaving the car off for about 2 hours the car will start again and could be driven with the sports or manual mode intermittently inoperable.

Sounds like a communication issue to me but not really sure where to look at. I also dont have access to the wiring diagrams at the moment.

Would really appreciate your guidance.

Thanks
Joy
E53 4.8is 2005 at 223000km




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Tried checking with INPA again while the engine is running but still there is no response from the gearbox control unit it says. Car can be driven but no sports or manual mode option. 🤕🤕


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Found this
Intermittent No Start, Transmission Failsafe Mode, Engine Shut-off - Bimmerfest - BMW Forums

I'll update later about progress........

Sounds like a dead battery.

I forgot to mention that - battery is brand new!

What's the voltage on the battery when connected to the car?

What's the voltage on the battery when the car is running?

12.3 ignition on
13.8 engine running
Battery is brand new - Bosch S5


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I would look at the cable that is attached to the TCM. Could be corrosion in the connector terminals.

Well the X would always start now. Error message is gone for now.
upallnight is right, it was just the connector to the TCM.

Now, on to the next problem!! Looks like a front diff change is coming!!!

That didn't last long! TCM is not responding again.

Is the TCM connector supposed to be dry? I notice the contacts always have oil in it when I pull the connector out.


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If it happens when your idling in park for like 5-8 minutes and it goes to Trans Fail and when you start it back off it goes away...that's what happened to mine 2002 ,it's the neutral safety switch.

Rockit, I don't really get a trans failsafe message. Symptoms are there is no sports and manual mode, and there's no response from the control unit when you try to access it in INPA

I'm thinking that the oil in the connector when it's plugged causes connectivity issues with the TCM or something.


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Where is the oil in the connector coming from? Get some contact cleaner and get it out.

Most likely a failed seal. Probably this o-ring

https://www.ecstuning.com/b-genuine-...s/24101423176/

Not really sure where the oil is coming from.



Does this mean I have to open the tranny again??





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Yep

Bugger!


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