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HELP: P/R/N/D has vanished from my display...without three bars of death! Car won't start or move out of P.(TCU)

6243 Views 26 Replies 10 Participants Last post by  Sal marinosci

2008 fortwo cabrio with 49k miles and a fresh battery that was just tested.

Worked fine all day...then PRND on dash display. Also won't start or switch out of P. Yellow button trick allows it to go to RND but still won't start and locks up again once put back into P.

Doesn't turn over or even try to start. It is as if it can't see its transmission.

Swapped clutch actuator... no difference. Checked main fuse...load tested change. Edit: I plugged in my relatively simple/cheap OBD reader and it showed no faults.

What would make the PRND disappear?

Thanks, -Eff
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I can't believe I forgot to say this: I plugged in my relatively simple/cheap OBD reader and it showed no faults.
The fault may be in a system it can't access.... :)
Any recommendations for a better reader?

Rather than try and DIY this, my recommendation is find a local shop that does Mercedes work and has a Mercedes STAR machine and let them check out the car. It may cost a little more but they can pinpoint the problem and save you money in the long run. Just my .02. :)
Thanks. That is a good point. I am new to all this and didn't realize folks other than M-B had those. Makes sense.

Might search a few more things (disconnected connectors?) before towing to a shop. But sold advice.

Probably time I grabbed one of these as well. For the future.
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Edit: I believe the MB v2.0 supercedes the MB II.
Good call. Just reached out to Amazon and swapped for the V2.0. Thanks.
I had the PRND disappear on me a few times a couple of years ago. My forever remedy was the good ol' tranny retraining routine. Probably ran the routine 10 times that night, and a few more times the next day lol. It worked. (psst! I also sprayed some lithium grease into the shifter motor omg... don't tell anyone)...
My car won't start. Was your car running when you did this?

E, yes, it was running. I noticed that yours wasn't. Umm, could it be that your starter died at the same time your car couldn't see the PRND? It would be a huge coincidence, though.
I'm assuming the car can't see its transmission and accordingly won't start.
Icarsoft arrived. I ran diagnostics and these 3 fault codes appeared.

Any ideas?
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Thank you. If I end up swapping it out, do I need to get the car to the dealership to reset/reflash it? Thanks!!!
The first thing I did was swap the actuator. No difference.
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The transmission control module is under the carpet under the drivers seat. Disconnect your battery and remove the key from the switch. Unplug the 3 connectors under the driver seat. Remove all 4 seat bolts and then fold up the seat and remove. Don't reconnect the battery or turn on the ignition switch with the seat connectors unplugged or you will trip your SRS (airbag) light. Clean the connector on the module. It is in a good space to get wet if the carpet ever got rained or spilled on. Either the connections are dirty or the module itself is bad. You can find used modules on ebay or Autobahn recyclers online. DCO
Welp...15 months later, I bought a 2nd hand TCU and did as you said. Car drives perfectly now. Thanks!
Sky Vehicle Car Cloud Motor vehicle
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It looks my dashboard after the TCU was broken. I have a Smart 2008. well.

Car did not crank. I posted symptoms and how I got it fixed.
You may want to check it out.
You called it too!
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