Is the CEL on? Any number of issues like a bad conductor plate or oil leaking into the TCM could cause the transmission to go into limp home mode as you describe. Without a scanner it's really impossible to diagnose.

 

 

Buy it. That's exactly the situation I bought my c320 wagon in for $1100. The previous owner had the mechanic replace the conductor plate, solenoids and plug. When that didn't work mechanic told him it needed a new transmission at which point he gave up and sold it to me. It had ATF in the TCM which the mechanic neber bothered to check. 722.6 is very difficult to kill especially with a little 4 banger.

 

 

Pulled up the carpet and cover in the passenger foot well to find the TCM covered in ATF. OBD2 had a code for no trans communication. I got an icarsoft i980 to scan the TCM, no communication. Removed the TCM, removed the oily circuit board from the case and bathed it in isopropyl alcohol. Same with the case, plug etc. Reinstalled it and still no coms. Removed it again and reflowedthen the large solder joints where the PCB meets the plug. At that point the transmission came back to life with butter smooth shifts. The ATF had gotten into the microscopic cracks in the large solder joints. Once reflowed it was good as new. I've put 14k miles on the car since the repair.

 

 

Yes that's exactly the reason. The fabric like tape they wrapped the harness in functions like a wick pulling the oil towards the TCM. Some people just ignore the leak till the TCM stops functioning.

 

 

Control module


Pull of the cover to check for oil contamination but didn't detect any visible signs.


No oil contamination visible


ICarsoft CR Plus code P2500


Code P205A-008
Good day to all.
Impressive work there.
I've not been so thorough as you, but I'm learning. My problem started after i changed the ATF on Tuesday evening and carried the car for a test run in the neighbourhood. I bought the car at 68,600 miles.The tranny oil and filter were changed at 79,000 miles. Only got to change it again at 130,100 miles day before yesterday as I realized about 2 months ago on fairly long weekend trips of over 60 miles in one direction, the tranny will not shift smoothly on hills and country roads with lots of S bends. Changed the oil and filter and the car was stuck on 1st gear. Yesterday my brother (an indy mechanic on mostly Japanese vehicles) came and suggested that we go for a slow drive. The tranny started shifting after about 1/2 mile and was shifting smoothly after 6 miles.on a country road. I live in Trinidad; the car is a RHD W203 C200 Kompressor. After we came back home he left and I decided to run a errand. On the highway the car suddenly went into neutral at 50mph for a second then back into drive with a jerk and the engine light came on. So it's in limp mode and not shifting beyond 2nd gear now. Used my iCarsoft CR Plus Scanner and got the following Codes P2500 and P205A-008.
{I also have a left and right wheel speed sensor issue (P2302A-001) before the oil change but that's for another thread}.
I can try re-soldering the large pins or purchase a module and conductor plate which will take just over a week to arrive.
I'm not bothering with the MB agent as I've met their service technicians buying Febi Lemforder and Bosche parts from a general parts dealer just one block away. The general parts dealer doesn't have the parts in stock at this time.

 

Did you pull those codes from the transmission computer or engine? It sounds to me like you have a bad conductor plate or solenoid.

 

Thank you very much for your kind response.
In the Diagnose Process window, there are four items:
(1)Transmission
(2) ME-SFI-Motor electronic.
(3) ESP
(4) AB- Airbag.
Transmission gave me the P500 code and the ME-SFI gave me the P205A-008 code.
Oh, one more thing. I tried driving the car about half hour ago and this time the transmission went into neutral at 30mph while in 2nd gear. The rpm climbed to 4000 and won't cross that mark. As I backed of the gas, 2nd gear engaged then down shifted to 1st gear somewhat fierce. As I applied gas it went neutral again. I stopped the car, manually selected 1st gear and drove off, but it won't exceed 4000 rpm. Put it back in drive and went back home with it going only up to 2nd gear. Fortunately I was only 1 mile from home.
I can ask my brother to pull down the valve body and let him check the solenoids while I purchase a conductor plate. But I will have to wait until he's free this weekend.

 

I'm Back with a positive update.
I bought two new wheel speed sensors but car was still stuck in limp mode. Bought a used TCM for $42.00 and a Yaw Rate Acceleration Speed Sensor for $26.75 on eBay, but car was still getting stuck in limp mode. I was able to drive over 300 miles on the highway and country roads with the transmission sticking on 1st gear for a 1/4 mile after start, then settling down to a fairly smooth drive going up to 4th gear. (no 5th). Gas mileage with a/c on was average 24 mpg based on instrument display.
But I did a lot of reading in this forum and viewing YouTube. I didn't purchase the conductor plate nor pulled back down the valve body as I sensed from the clues I gleaned, that such an undertaking wasn't necessary yet. I just felt something was missing. Then I got a ABS light as soon as i started the car a week ago. The scanner showed ABS pump fault code C1310. But it also showed a stored left rear wheel sensor fault. So I bought the whole ABS unit on eBay for $75.00. My wife helped me bleed the brakes until I got new brake fluid coming through the clear plastic line I attached on each of the four wheels, bleeding one wheel caliper at a time.
That was Saturday evening. The car was still stuck in limp mode so in desperation I prayed and asked the Lord Jesus to help me, show me what to do. What is the source of the problem? Well he did show me in a dream.
So yesterday Sunday, on the way to church, I hooked up the CR Plus scanner, set it to Transmission; Live Stream Data; "speed sensors" and asked my wife to read out the display for the four wheels while I drove.
She indicated that the left rear wheel speed sensor display wasn't changing. That was the problem. The new left rear wheel speed sensor was defective. Borrowed a digital multi-meter from my work place this afternoon and checked the sensor on my arrival home. The reading confirmed that it was faulty at 0.49 m ohms, both directions reversing the test leads. I put back on the old speed sensor that usually faults after about 30 to 40 miles driving. I then cleared the existing codes and asked my wife to join me again and read out the display. The car ran smoothly from 1st gear to 5th gear with all four speed sensors working. The rear left speed sensor did give a flicker for a moment and brought up "implausible". Switched off, restarted and drove back home with no fault codes. Just before reaching home, I stamped the gas from standstill and the engine revved quickly and smoothly all the way to 6500 rpm. Backed off the gas and still no fault codes. Thank you Jesus.
I'm going to buy a new left rear wheel sensor in the morning.
I must also thank all the posters who wrote their experiences and those who gave advice on this very helpful MB.org forum. Keep up the good work.