ron m.

This is the second time this year that my TCM decided to lose its mind and let go of the transmission at freeway speeds. The first time it happened, I accidentally cleared the codes (this was 4-5 months ago). Today, it happened again and the codes were P0700 and 720.

Would cleaning the TCM connectors and harness be a possible solution to my gremlin (I know someone spilled beverage on my shifter area no more than two years ago)? Are these units flaky?

Just to share my experience, once the TCM let go of the transmission coupling to the engine, there was no way to re-engage it while cruising. You have to pull over, turn off the car and turn it back on again. I suppose I could have done that in neutral while coasting but probably not a good idea to lock your steering wheel OR engage the tranny at freeway speeds.

ron m.

Hmmm... so no one had a similar experience? Weird.

Musikmann

That has never happened to me but I don't think cleaning the TCM will hurt anything and it might even help. I also think they are flaky by nature but once some liquid is spilled on them they can get that way quickly. Have you found a source explaining what the error codes are?

ron m.

My code reader has the explanation for the errors (you can also google them). The first one pertains to a transmission fault and the second one pertains to speed sensing (relative to rpm I think).

I've read in previous posts that you can actually get codes from the TCM through the dealership. I might do that.

saintz

After a quick search, it sounds like that's an issue inside the transmission. However, cleaning the shift module probably won't hurt. There are some posts on here about it, but basically you disassemble everything and spray with some contact cleaner (some people use rubbing alcohol and a q-tip).

Can you describe what exactly happens when it "goes out"? In particular, if you floor the gas pedal (all the way down, so it depresses the switch on the floor) does it cause the problem? When it's out, is it truly out of gear, or is it in gear but very unresponsive (push gas, car waits 5 seconds, then very slowly accelerates)?

ron m.

What appears to happen is a total disengagement of the transmission. It's like you're in neutral and when you rev the engine, there's no tranny that couples to it. Going to neutral and then shifting through the different gear settings does nothing either.

Once on the side of the road, I turn off the engine and restart. Then, Viola! I'm back on the road again with NO SIGN of transmission problem... shifting is smooth, rev is okay.

armaniE55

I'm definitely going with TCM but this one will be tuff to diagnose. Speaking from experience of course (spilled Redbull on mine, yes I know Ohlord no more drinking Redbull in the AMG). I hate to say it but this one may need to go to the stealership to at least troubleshoot the issue with one shot.

My .55 cents

Good Luck and keep us posted

TMAllison

Your OBDII scanner is only pulling generic codes. SDS or another similar scanner will read the underlying codes and adaptation values and point a good tech to the problem.

sunny61

This just happened to my 97 e320 yesterday. I was going about 75mph and when I floored it to speed up and it felt like the tranny attempted to downshift but never engaged. The SCARY part was that the engine REVed to +4500rpm and stayed reving 4500 even though my foot was not longer on the gas pedal... it did this for about 5-10 seconds and then shifted into gear on its own. It never happened again but now I am a little worried.
My car has been shifting very rough going from 1st to 2nd and 2nd to 3rd for the past 2 weeks.
Does anyone know if these are signs that the tranny is failing? do a lot of trannys fail on these W210s? I have 110k miles and was planning to so the tranny flush but now starting to second guess whats best for the car. Should I just leave the tranny fluid as is or replace it? Any chance the flush can introduce new problems?

sunny61

.... Fixed my problem was the MAF sensor.

Red66GT

Had a similar incident with mine a few months back and got a PO715 code. I was driving around 65mph basically in 1st or 2nd gear. Unknown to me, the tranny would not shift. I think the motor started hitting the rev limiter as I was losing power so I pulled over. I shut the car off, then started it and started pullling back onto the road and that's when I noticed my tranny was not shifting. It was stuck in a single gear and reverse would not engage. I limped it home taking side streets...took it in for service the next day. They had to replace the circuit board that is in the tranny. Been fince since.

I did have warnings this was coming though.....my tranny would slip into limp mode every once in a while. Not sure if this is the same symptoms as you as I got a different code.