Hey guys, i really hope to get some insightful thoughts on the problem i'm facing with my 2013 ML 350 from some of the forum's experts. XD
Every once in a while (say every couple of weeks), my ML switches Gears once after ignition from P to say D or R and then gets stuck in that same gear, for example: I turn on my car and i switch to R and back out of my driveway and then once i'm in the middle of the road and want to switch to drive, the car won't budge. I can only switch back to P and then i get stuck in P position. usually switching the car off locking it and then unlocking it and switching on fixes the issues and i can shift normally again.

After reading lots of threads, i now know that the two batteries are the first thing to look at , however both AUX and Main battery have been changed less than 2 years ago.
second culprit: The Alternator: the IB (amperage) reading reads +20 Amps approx (so it is charging the battery) with the car on however i do note the the value fluctuates depending on the driving and the rpm of the vehicle.
3rd - SCM steering column module : i would be so happy to know if one of the previous users who fixed the stuck in P issue by only changing batteries if he/she was getting the code U1420 can communication with the control module"N80 (scm/mrm)" is faulty
in addition to the P172A00 - The direct select lever is faulty. BASICALLY what i want to know is if these codes show up even when the problem is due to the main or aux battery age or bad voltage.
4th- Finally i also read in one of the threads that the ESP/ABS Control Unit could cause the Selector not shifting issue, i once did have a stored code regarding the ABS ESP unit but i deleted it with my scanner. Not sure if that's where my problem resides.

I hope to get some feedback from you guys.. Any help is appreciated.

 

this info is after reading many threads on the subject. Your aux battery was it fully charged when installed? A lot of times people found you need to trickle charge the AUX BATTERY BEFORE install.
second thing I can recommend is resetting the ECU.
from this thread
https://www.benzworld.org/threads/w1...tions.2732961/

After you are finished reinstalling the new battery you now need to reset the ECU or your ML350 will not switch gears out of park. I cannot believe that this is not in the owner's manual. Here are the steps to reset the ECU:

- If you have Keyless Go, pop off the Keyless Go button
- Insert the key
- Turn the key to "ON" - not start - and leave it "ON" for more than 2 minutes
- Turn the key to "OFF", but leave the key "IN" for at least 10 seconds
- After at least 10 seconds, turn the key to "ON", push and hold the brake, turn the key to "START" and the car should start. Verify that you can switch gears.
- If you have Keyless Go replace the Keyless Go button

That's it.

 

Thank you for your reply Ml350maf

The case you are talking about is if the car wouldn't shift gear after a recent battery change, and in that case if i understand correctly the car wouldn't shift out of P at all. However in my case the battery in the vehicle was changed almost 2 years ago and the car switches out of P normally almost 99% of the time.
my current doubts are directed towards either the ABS/ESP control unit or the alternator. The reason why these are the main targets now is 1: the ABS ESP control unit had a fault code on the scanner a month ago but my mechanic cleared it. And I read somewhere on One of the forums that a faulty ABS ESP unit could cause the stuck in gear problem. And regarding the alternator when I open the service screen in my instrument cluster I monitor the voltage and the current of the vehicle while driving and I notice that the current fluctuates a lot while driving from -10 A to +40 A And the voltage of the battery keeps going back-and-forth from 14.5 V to 12.5 V while driving (can someone confirm is this is normal behavior?).

 

When the engine is running, this measurement should be 13.7 to 14.7 volts. Turn the lights and radio off to see Amps change.

 

Likely the steering column “module” needs to be replaced. This is the device including the direct select lever, turn signal and was what formerly known in the old days as the “clock spring”.

I forget what MB calls this. Search the site, this comes up now and again. It seems to occur on 166 more than other platforms. Maybe the supplier is unique to 166 vs other MB models.

Have you had the transmission service done by a dealer or Indy shop? This is mandatory on MB boxes.

 

Hello chassis,
Thank you for your reply
I do understand that the problem could be lying in the steering module itself, however the multitude of intermittent issues that are occurring with my vehicle (abs fault code flashing for 10 seconds then everything going back to normal on its own, stuck in park every 40 to 50 ignitions..) lead me to believe the issue is an electrical one.
I just came back home from an appointment at the mechanic and i explained to him what is happening, he instantly told me that it is not normal at all for the voltage of the battery to drop to 12.5 while the car is on and driving it, so the first thing he looked at was the alternator which was working fine most of the time, he proceeds to unplug the voltage regulator (comes attached to the alternator) and after he unplugged it (for troubleshooting purposes) the voltage was constant at 14.1 (not even a 0.1 fluctuation) while the car is on. So he told me that it was almost certain that the regulator was faulty and was causing random electrical faults in my car including abs/esp flashes, selector stuck from time to time, and some other electricals tweaks.

Can i get your thoughts? Should i proceed with changing the regulator? Was the troubleshooting process reasonable for you?

 

Regarding the the transmission service you asked about, i have only owned the vehicle for 1.5 month and i only changed the transmission fluid as transmission service upon purchase am i missing something?

 

Transmission service = fluid replacement. Who did the fluid replacement?

Transmission electrical issues can be in the steering column module or the conductor plate. You need to diagnose the source.

Replace both the main and auxiliary batteries. Sounds like this car may not have been fully maintained. You said the batteries are 2 years old but you have owned the car for 1.5 months. Please explain.

 

The transmission fluid replacement was done by a certified Mercedes workshop upon purchase of the vehicle.

regarding the batteries, after reading multiple threads it was clear that the first culprit to look at were the two batteries so I went ahead and checked both the batteries and I found that both batteries had a stamp of production date in early 2020, so assuming the worst case scenario the batteries would be two years old.

and for an update regarding the voltage regulator, I’ve had the voltage regulator disconnected for two days now and as I said earlier in the thread that before disconnecting the voltage regulator I used to have weird fluctuations in the current (sometimes the current drops to negative values, that means the vehicle is withdrawing charge from the battery which is so weird to happen with the car ON) and voltage of the vehicle while it being on and driving the vehicle, However after the mechanic disconnected the voltage regulator for troubleshooting purposes, the voltage of the vehicle has been constant at 14.1 while driving for 2-3 days, and no gears stuck issues throughout these 2 days.

 

What are you saying?

You are operating the vehicle with a portion of the alternator disconnected?

 

Yes, as I'm trying to pinpoint the issue.. And apparently it is truly the regulator that's cause the weird voltage fluctuations in the vehicle and therefore leading for the gear to be stuck in position. Waiting for the new voltage regulator to arrive and will install it immediately. And i will give you guys an update on the matter.

 

i have finally fixed the issue ( 2 months problem free so far) posting a detailed troubleshooting process soon..