cwallens

Hello everyone,
hopefully someone can help me because I am really desperate. I am driving a 2001 S500.

Symptoms:
- first I realized a power loss and that the transmission shifted weird. After I stopped, I couldn't get out of D anymore (I couldn't pass N into R or P). I found out that when I release the brake I could shift it into P.
- after I started the car again, everything worked great for over a week
- it started to happen more frequent
- I checked the transmission fluid and it was just a little bit low so I filled it up again (less then 1/2 a quart) and it seemed fine for a while
-it started again and now it is almost every time I drive the car and sometimes I simple restart of the car won't solve the problem anymore
- Check engine light came on (Error code: P0705 Transmission Range Sensor Circuit malfunction (PRNDL Input)) --> no clue what that means
- I also realized that when there is an issue, I can't change gears manually
- Sometimes the gear indicator (DS or DW) in the cluster instrument doesn't indicate that I'm in P,R,N, or D. It is just black.
- I reset the error code a few times by now and sometimes it seems to help but only for a short period of time
- no transmission leak
- transmission fluid is fresh and I have the correct amount of fluid

What could it be?
Like I mentioned, the transmission is completely dry (outside) so there are no leaks at all.
I did some research already but I couldn't find out if there is something like a Transmission Range Sensor. Is there something like a sensor (I also couldn't find one to buy)?
Also, could someone please tell me where the Transmission Control Module is located and if I get a new one, do I need to get it hooked up into the bus system by a Mercedes shop or is it just "plug 'n' play"?
Is there a way to reset the transmission control module? I checked the pinned "Start here" threat but I couldn't find anything. Maybe a reset would help the issue.
I saw in a few other threats that some have issues with oil inside a connector. Where is this connector located and if there would be oil in/around it, I'm sure I would have seen a leak somewhere ???

Thanks everyone in advance for your help, you guys are awesome!

Please help me with my baby...

Chris

MB-Dude

I did a simple Google search for - Mercedes P0705 code - and found a plethora of information. This one is problem the best link... http://engine-codes.com/p0705_mercedes-benz.html
Looks to be neutral switch related.
Cheers,
Jeff

ibeforreal

Could possibly be your transmission conductor plate. Take a look at these very insightful videos about the transmissions in these cars. I believe there are six videos in total. Here is a link to the first one.

cwallens

Thank you everyone for the information.

update:
I pulled out the transmission control unit and I poured out about a shot glass full of oil. I have no clue how it got in there. Now I'm trying to open it up and clean the circuit board with electronic cleaner.

Does anyone has a clue how I would get this much oil inside the TCU?

Thank you,
Chris

ibeforreal

The oil has been been known to wick up to the TCU. You should probably replace your conductor plate and the plug.

GrepAwk

Chris:
How did you get access to your TCU? Where is it and what did you have to move/remove to reach it? (I haven't explored under my carpet or console enough yet to know.)

The source of the oil you found in your TCU is the electrical signaling cable coming up through the belly from your transmission. The leaky ring connector on the corner of the actual transmission housing, to which you referred earlier, is the same culprit that lets transmission fluid bypass the seal inside where all the pins connect. Once the fluid gets into sheath of the cable bundle, into the actual wires in the cable bundle, capillary action allows the fluid to wick upward toward your TCU. It gets to the TCU and then fans out among the electrical components.

There are a few threads in this forum that explain it. Clean the TCU well, soak up as much residual oil at the topside connector, and change out the plug/connector at the tranny.

cwallens

update:
After cleaning out the TCU with fast drying electronic cleaner, I put everything back together. I reset the codes and so far it is working great. I still ordered the new connector and will replace it as soon as it gets in.

GrepAwk:
The TCU is located in the left fuse box (passenger side) right below the windshield. If you open the fuse box, the TCU is located on the side closest to the fender. You'll see to connectors attached to it. I unplugged them and pulled the complete TCU out. I used a thin flat head screw driver to carefully pry open the plastic housing and the circuit board will come out. I used fast drying electronic cleaner and cleaned the circuit board and all connectors really good ( I used 2 cans to make sure everything is clean). I hope this will help you.

The new connector should come in on Thursday and I'll change it out to make sure that no more oil will wick up into the TCU anymore

wallyp

"...left fuse box (passenger side)..."

The TCU is in the right fuse box. Left and right are always defined from the point of view of a seated driver. The left headlight is always the left headlight, whether you are standing in front of the car or behind the car. Same with the left fuse box.

cwallens

update:
After I realized that I most likely lose a lot of transmission fluid when I open the connector I have decided to open the transmission, take out the valve body and replace the conductor plate as well.
labor was about 3 hours, but if I would have had my own jacks ( for proper space underneath the car) the job could be done in 2 hours. I wasted a lot of time with crawling in and out and trying to find the tool that I just put down a second ago.

The videos that are posted above helped me a lot to change the connector and conductor plate and it was an easy job.

So far the transmission is working great.

Thanks everyone for the help

ibeforreal

Glade you got it working again.

mashehab

I have the same problem with my 2006 S430 4matic ODBII Code P0705 with same symptoms scanner says transmission range sensor, I’ll follow the same procedure you did and will let you know what happens.

wallyp

I would strongly recommend just cleaning the TCU first, then driving the car for a few trips to see what happens.

Kebowers47

it is leaking through the electrical connector to the transmission. The connector needs to be replaced. It is low cost, less than $50, and R&R is quick and simple, but does require removal of the oil pan.

wallyp

"...but does require removal of the oil pan."

Nope. The connector that leaks can be replaced from outside the transmission, with very little loss of fluid.

Tim44

After extensive searching I found some Russian Youtube videos showing poor solder connections on the TRRS module optical detector IC's. They resoldered the chips and repaired the gear selector module which is responsible for the P0705 codes. I gave this a try and it worked. The optical sensors are TCPT 1200 devices see the attached pictures. .

These are the 2 sensors for the slap shift D +- -

TRRS module ,note the 4 PRND optical devices. when removing this module remove the 2 T25 screws and slide towards the rubber cover then lift up.

Shift moduke