jshish

Hey guys,
Just till the other night I had the original battery on 2002 C240. About month ago the car started giving me an error with the light sensor after the first start in the morning. If I shut down ad restart, the error almost always went away. I figured out it is the battery that needs replacement therefore it wasn't anything urgent as the car was still starting fine. One day about 2 weeks ago I started the car and i got again the light sensor error, but also the transmission shifted harder then usual and after few hundred feet of driving I noticed it was stuck in 1st gear. After I drove few hundred yards (as soon as I figured it out) I shut the car down and then restarted. That brought it all back to normal. I attributed that incident to the low battery voltage and decided I should change the battery as soon as I can. The car drove fine for the next 4-5 dais then I left for a business trip and left the car on the airport for a week.
As i returned from 1 week business trip, and i started the car to get home. As expected I got the light sensor error, and ASP error(ASP error happened once before too so wasn't unexpected and it goes away after restart), but this time as I shifted in "D" it was harsher shift then the usual soft shift and my engine light came on. There I was in "limp mode" again. I tried the the usual cure and restarted the car, but no luck this time I needed to drive home really slow...

Same evening I replaced the battery and all electronic errors cleared up right away, except the engine light and the transmission was still stuck in "limp mode". That same evening I disconnected the ground of the new battery and left the car with no power overnight. The next morning I reconnected the car and started the car. The engine light did come on after I started the car. This gave me hope. Unfortunately not for long, as soon as I put the shifter to "D" I felt the harsher than the normal soft engagement and few seconds later the "check engine" light lid up again. At that point I decided to spend few bucks with the local MB dealer and get the problem diagnosed. The long story short - after 2 1/2 hrs shop time and $350 out of my pocket for the service, I was told that there was a problem with a electrical plug on the transmission and ATF went up the harness to the TCU. According to them the TCU as well as the whole electrical harness and the connector needed a replacement. What kind of crap is that? They said it is $991 for new TCU and about $270 for new harness. At this point I just drove my car home in first gear as I thought there is no way I will pay them 2k to repair this problem that appeared to me is "make work" for the dealer. My transmission always has been in perfect shape with soft engagement in gear and nice and crisp shifts. I use to run a transmission shop 15 years ago and while little rusty, i still have good judgement for the health of transmission.
Tonight I dismounted the TCU from the car. There is little bit of ATF up to the connector of the TCU, but not much at all. The dealer theory was that the ATF was under pressure therefore got into the TCU and fried the electronics. I carefully pulled the PCB from the TCU box only to find out that there was no ATF contamination inside what so ever! The TCU was so sterile inside as it was when it left Siemens factory. Of course I cant be sure that it works but i don't want to spend thousand bucks for new one just to find out that the same problem with the car is still there. Can anyone help? PLEASE? Where should i start? Any one with similar experience?

jshish

forgot to post it above... here is the diagnostic printout from the dealer

Glyn M Ruck

Lots of experience on this board of this problem.

Replace the electrohydraulic bush & stop leak $8 part at RMeuropean. Clean up oil in harness. Once that is done go from there. I'm sure it will fix it if no oil has entered the TCU. At worse you might have to replace the harness. They are getting all sorts of crap readings because the oil is causing partial conductance between the pins/wires in the harness & plug. Pray the TCU is not damaged - unlikely if dry.

https://mbworld.org/forums/c-class-w...sues-help.html

pcy

For all 3 vehicles ('04 C320, '07 C280, '98 ML320), I have replaced the pilot bushing on the trans as a preventive measure. And, every time the car is on the hoist/lift, the first thing I check is the pilot bushing to see any signs of trans fluid leakage.

I carry one extra pilot bushing ready to be installed when I see any signs of oil leakage.

Javvy

good advice from PCY and Glynn, change the pilot bushing and clean the harness or replace it. I think this will solve your problem.

I had to go through the same and it was the pilot bushing that had shorted, ever since then I have bought 2 extra ones and keep it in the car. If the symptom arise again will go atraight to the pilot bushing first and if I get an oppurtunity to peek under if on a hoist will check this bushing the frist thing..........

goodluck....
javvy

Glyn M Ruck

+1 pcy. I have a spare in my glove box in it's Benz packaging. Funny thing is with a spare - NO LEAK. $8 insurance