Hello all,

I drive a 2002 C240. It started getting stuck in the 1st gear about one month ago.

I posted a message about this problem here: https://mbworld.org/forums/c-class-w203/236336-c240-gear-does-not-up-shift.html

Couple of people suggested a weak battery. I purchased a new battery but was too busy too install it.

Two days ago the engine light came on (for the fist time), and the transmission got stuck again in the 1st gear. As usual I tried to switch the car off and on but unfortunately this time it did not help. The car jolts backward or forward as you move the shifter from R to D and while in D, the transmission does not shift out of the first gear.

I changed the battery when I got home. Immediately other errors due to a weak battery that have also been reported in this forum went away, but the main problem has not been resolved. The transmission does not up-shift anymore and the check engine light in on.

a) Can a weak battery cause a permanent damage?

In my previous post, someone suggested that "In addition to a weak battery, you could also have a leak in a transmission switch, and transmission fluid has wicked up the cable and filled the transmission control unit with fluid". I should mention that I have not experienced any transmission sleeping which is apparently a sign of transmission switch leak. I also checked the transmission fluid level and it seems to be OK. I have not accidentally pured any liquid on the shifter area as well which have been reported to cause such problems.

b) Can anyone instruct me as to how I can check for a leak in transmission switch or in other places?

It is very frustrating, I don't trust the dealership in Ann Arbor so I am not willing to take the car there and the next nearest dealer is some 30 miles away. I would like to educate myself as much as possible before taking the car to a shop.

c) Does anyone know a trustworthy repair shop in Ann Arbor area?

d) And finally where I can purchase a device that can read the error codes?

Sorry for the long post. I have tried to be accurate with my description hoping that someone could shed some light on this issue.

Thanks in advance.

Hoo121

 

How many mile do you have?
Have you done a full flush of the tranny yet?

 

I agree, what maintenance has been done on the transmission? I looked in my maintenance book, and I didn't see any recommended service intervals on the transmission.

 

Thanks for the fast response. I have 46,000 miles on the car, no work has been done on the transmission.

Thanks,

Hoo121

 

You need to pull the OBD II code associated with the CEL. Your transmission could be in 'limp home mode' and there's nothing wrong with the transmission.

 

You may want to look at this thread if your car is shifting strangely:

https://mbworld.org/forums/showthrea...288&highlight=

My C240 was downshifting at the wrong time - I would cruise at @ 25 MPH and it would down shift to first. Ended up being the control unit - once replaced it runs fine.

 

Hello All,

Regarding c240 transmission problem, I went to AutoZone and they checked the OBDII error code for free. It is P0702: Transmission Control System Electrical.

Any suggestions would be appreciated.

hoo121

 

I believe that unit is in a compartment under the front passenger mat? If the trans plug leaks....there's a TSB on changing the O ring ....the fluid migrates up the harness to the TCU. Lots of posts on this.

 

Thanks for the fast reply. Someone suggested that if this happens, the transmission would skip, I did not have this issue, before the car went into limp mode.

I however would like to check for this problem, can I take apart the TCU to see if this is the culprit? Any pictures or instructions would be appreciated.

Thanks,

hoo121

 

I had this happen to me, It is your electronic shift plate. It cost me roughtly 600 at the dealership for them to fix it. Its just basically the sensor that lets your car know when to shift. When the RPMS reach a certain level. I know this because it happend to me twice.

 

Search this forum........

 

Thanks again for your replies,

mleskovar: As you suggested I did search, this is what I found: http://www.installuniversity.com/mb/...ans_oring.html

Jah Know: Thanks for the suggestion. Do you mean Transmission control circuit? Do you have the part number for it?

Regards,

hoo121

 

That's the biggest cause of the failure....search some more and I think you'll find where someone removed the circuit board and cleaned it and the harness after fixing the plug seal.

 

Hello All,

I finally took the car to an independent shop in Ann Arbor.
By the way, if you are living in Ann Arbor, avoid the dealer at all costs, I have many bad stories to tell about them.

Anyway, the shop checked the engine error codes, there were six error codes stored, they erased them all and limp home mode problem was resolved. All of the problems were due to a weak battery.

The sad story is that I had changed the battery last week, however, because of the stored codes, the transmission would not come out of limp mode.

Shame on Mercedes, it baffles ones mind as to how they designed their electronics.

So Please beware: A weak battery can cause major headaches. Even after changing it with a new battery the problems may persist because of stored error codes. Furthermore, there seems to be no reliable way of erasing the error codes by yourself (I believe I tried everything based on what I read in this forum including disconnecting the battery overnight) unless you buy an OBD II reader or take the car to a shop and pay $90 for troubleshooting.

Thank you for your replies and suggestions. I have learned a lot on this forum.

Regards,

hoo121