Help with transmission parking lock fault 4ec8

[Pruzina]

SOLVED
For someone with same issue in the future.
It ended up bad parking position sensor. Which is not that surprising because that's exactly what the fault code said. But to fixit you need to code new mechatronic to the car which is for most not at home job.
So basically took the mechatronic from the donor transmission my old mechatronic and had it coded to the car put everything back together and works like a charm.

Original post.

5 out of 10 times when you press P to engage parking it will show transmission malfunction...transmission position P may not be possible.... CODE 4ec8 position sensor.

Well I set up my camera under the car and watched what is happening.
When P engages as it should the lever on the side of the trans for emergency neutral moves smooth as it should.

When P doesn't engage as it should Flashing N and trans malf. The lever moves in like two steps it moves stops for a split second in the middle and then goes all the way.
So the parking lock is actually engaged but as it takes longer as it should malfunction pops up.

I've searched everywhere and there is not one word on internet about something like this.

I've spent hours taking apart my spare transmission to figure out how exactly this locking mechanism works trying all movements. It's actually pretty simple mechanism can't find what could be wrong.

Even swapped few parts from the other transmission no change at all.

I have few videos if interested. I would be really surprised if some ever came across this issue or know how to fix it.

[Sophisticated Redneck]

Originally Posted by Pruzina

5 out of 10 times when you press P to engage parking it will show transmission malfunction...transmission position P may not be possible.... CODE 4ec8 position sensor.

Well I set up my camera under the car and watched what is happening.
When P engages as it should the lever on the side of the trans for emergency neutral moves smooth as it should.

When P doesn't engage as it should Flashing N and trans malf. The lever moves in like two steps it moves stops for a split second in the middle and then goes all the way.
So the parking lock is actually engaged but as it takes longer as it should malfunction pops up.

I've searched everywhere and there is not one word on internet about something like this.

I've spent hours taking apart my spare transmission to figure out how exactly this locking mechanism works trying all movements. It's actually pretty simple mechanism can't find what could be wrong.

Even swapped few parts from the other transmission no change at all.

I have few videos if interested. I would be really surprised if some ever came across this issue or know how to fix it.

I would try replacing your solenoids if you have not already. I would do them all, not just the park.

[Pruzina]

Well after I went deep into the old transmission to learn how the whole thing works I've learned that basically the park lever is in resting position in park holding there by tension of strong spring. When you engage gear one solenoid push the lever and another solenoid catches it and holds it in unlocked position.
So if the solenoid would be bad it would not move from park and or stay out of park.
When you engage park one solenoid which holds it basically release it and the spring will make it go to park. Solenoid release it every single time without issue.

[Pruzina]

Well little plot twist!

Two step movement of the lever is most likely completely normal.
I put camera under my second X5 and found that the lever moves in two steps every single time and not showing any fault codes.
Which makes me believe that I was the whole time chasing wrong issue.

The issue is most likely either in the park sensor which is part of the mechatronic or some problem with the coding of the mechatronic.

Now I have to find someone who's able to code mechatronics.

[randall67]

Did you update EGS module with NC expert ? Do you have a working copy of ISTA/P ?

[Pruzina]

No I didn't update EGS. For 99% of things including coding I'm using protool as it's pretty straightforward and easy to do.
For the 1% I'm using ista. Never did coding using ista ncs expert or winkpf it scars me little bit.
Last thing I'd like to do is brick the transmission

[randall67]

The problem with winkfp is depending on your daten version it will update your module but will not digitally sign it because it is a Bosch when it should be a Lear. Due to its need to format the module before it updates it leaves you with a blank module and a world of hurt. I would honestly, and having done many before let ISTA/P have its head. Make sure you have a good battery maintainer so the voltage does not drop below 13volt. Run ISTA/P.
The beauty of ISTA/P is it will update the EGS module and all other modules that are related to the EGS module without you having to do a thing or guess what you may need. Remember ISTAP does to factory integration level, how it left the factory plus any update since. Maybe it is not electrical but mechanical but at least you will know.
I never let an E series car go unless I have a full final report from ISTAP. Coding with NCS expert is safe as a house and gives you far more options that Protool, bimmercode, carly etc. WINKFP for programming is not as safe as a house but it has its uses.
As mentioned it maybe mechanical. Do your paddle shifters work?

[Pruzina]

Thanks for all the explanation. But I'll let someone with more experience do the coding. I really don't want to end up with bricked transmission. Just made it back from Vegas today. so far it drives with no issues other than the fault

[Pruzina]

SOLVED. UPDATE IN FIRST POST.
Hope it will help someone in the future.