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)

6241 Views 26 Replies 10 Participants Last post by Sal marinosci, Dec 17, 2021

Effervescent

Discussion Starter · Jul 6, 2020 (Edited)

Howdy.

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

Worked fine all day...then suddenly...no 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 battery...no 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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Melvin Muckridge

· #21 · Jul 17, 2020

Effervescent said:
Howdy.

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

Worked fine all day...then suddenly...no 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 battery...no change. Edit: I plugged in my relatively simple/cheap OBD reader and it showed no faults.

What would make the PRND disappear?

Thanks, -Eff View attachment 63789

Short answer:
SACHS Slave Cylinder, clutch Actuator [3981 000 066]
my 2008 @49074 did the same thing,no 3 bars of death.
If you don't hear the servo when you turn the car to the on position this is the problem
Not hard to do and you will know the second you turn the key after replacement.

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Effervescent

Discussion Starter · #22 · Jul 17, 2020

The first thing I did was swap the actuator. No difference.

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recyn

· #23 · Jul 30, 2020

Effervescent said:
Howdy.

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

Worked fine all day...then suddenly...no 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 battery...no change. Edit: I plugged in my relatively simple/cheap OBD reader and it showed no faults.

What would make the PRND disappear?

Thanks, -Eff View attachment 63789

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.

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Reactions: 1

tomnytoys

· #24 · Feb 15, 2021

2008s have programing issues. My 2008 would work fine for days then all of a sudden 3 bars of death, no start constantly. Checked for broken wires, checked the switch in the shifter, transmission service and shifter motor clean.
Ended up needing a re-learn on the clutch actuator and re-learn on the shift motor. Works like new now with no problems. Any auto shop that has a AUTEL scanner should be able to do the the re-learn. Worked for me.

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Effervescent

Discussion Starter · #25 · Oct 24, 2021

DreamCarOwner said:
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!

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Effervescent

Discussion Starter · #26 · Oct 24, 2021

recyn said:
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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Reactions: 3

Sal marinosci

· #27 · Dec 17, 2021

Effervescent said:
It does.

Please disconnect your battery for at least 20 minutes or so, then wait at least 26 seconds before you try to start again after you reconnect it. I have a battery disconnect switch in mine for flat towing a nd it dose that once in a while after it is off. Good luck . Sal M

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