Been having a hard-shifting, funky trans issues. (45K on ticker).
STAR DAS reports adaptation values good, trans fluid is good, but is reporting P2500 ERROR "TRANSMISSION HAS IMPERMISSIBLE TRANSMISSION RATIO".

Dealer blames upgrades TCU, doesn't feel a flush is worth wasting $, and doesn't take transmissions apart, just installs remans.

From what I've researched, if it's a conductor plate, I'll get other codes, etc.
Not sure about purchasing a valve-body on a hunch due to the cost.

Any suggestions?

Have you ever hit your torque limiter? It will pop it in neutral and stay there until you cycle the key. It usually happens when doing a burn out. If so, It will throw that code. No big deal, just clear it.

If its your conductor plate, it will "usually" go into limp mode (2nd gear)and have codes for speed sensors (y3/6n3 etc..). Conductor plates are very common.

If you drop the pan and see metal, then you know you have a problem

No idea about torque limited since I'm third owner. There's SOMETHING wrong since it's clunking between gears (I think it's not shifting in time). No other codes though.
I guess I'll drop the pan and see what I can see. I don't know what else to do at this point.

Hard shifting in all gears (given that the fluid level is ok) usually points to discrepancies from from the speed sensors which are located in the conductor plate. Those same sensors also are used for calculating the "Transmission ratio" by the ETC. The discrepancy of the sensor readings might not be high enough to trigger limp mode and other speed sensor faults. I would start by dropping the pan and check for shavings, if you see any chunks of metal you can stop there. If all looks clean proceed to drop the valve body and inspect the conductor plate/ valve body. The speed sensors are magnetic and tend to collect alot of metallic crap which can affect their readings. Since you are in that far I would replace it regardless since is a very failure prone part and is the cheapest route to start with. Make sure the adaptation gets reset after you replaced/cleaned the conductor plate. Good luck.

Have the dealer swap your control unit #035-545-39-32 with a car that shifts correctly. My car displayed hard shifts between gears and after they replaced this control unit everything was back to normal.

Make sure you are using a dielectric transmission fluid.

Great advice from all...thanks. On the control unit: 035-545-39-32
Is this the TCU? It's $650 online so I'd like to be fairly sure before swapping it out.
Thx

I had this problem and the dealer told me i needed a new transmission for 8,500.
I then took it to a transmission specialist who checked it and said there was no metal shavings,and fluid was clean. I then had him change the conductor plate.
and i still had the problem. I then took it to a mercedes specialist and found that the ETC connector plug seal was leaking and filled the trans. control module with fluid I replaced the ETC conn. and instead of buying a new mod. I took mine out and sent it to a company call AES Automotive Electronic Solutions tele# 1-800-486-0922. for less then half the price. and i was all set.

good info

I am not sure, see if you can swap with someone local first to see if it fixes your problem.

I had the same issue and used this site extensively for information regarding my problem (p2500). After changing oil,filter and conductor plate i still had no joy with this problem. So back to the drawing board. The one thing i always noticed was that the box was experiencing no slippage and it was more common after the fluid had reached a certain temp. So upon removing the valve body for the second time and examing it a bit more. i found that the bolts holding the valve body together werent loose and at the same time they were not tight. i slackened off all these bolts and re-torqued them. I worked no more error and going strong. hope this information can help some one with the same issue as it was starting to become a pain.

Can you help me please
I have a ml63 AMG from 2007
And have eror 1936 ( Y3/8n4)

Can you help me ????

I presume that is the 7 speed 722.9. You need a new yellow thing (conductor plate/TCU replacement).