RAWAMG

Can anyone tell me where the TCU is located on a 2003 SL55? I need to get it out to send to my tuner

Also pics of the unit and/or the process sure would help

overZealous1

it is in the passenger footwell. on the side. one screw holding panel on. there is a couple detents holding tcu in and a little tricky to get to, but doable.

RAWAMG

Thanks OZ!

RAWAMG

Any advice about the detents?

overZealous1

my patience got the best of me and i ended up breaking one. but, the way they work it still holds the tcu back in. it is really hard to explain, but there is a detent on each side of the tcu that needs to be pushed in, then it slides out of it's tracks.

RAWAMG

LOL - it was a PITA but I got it... learned a little trick along the way... after you unplug it & while it is in the bracket pull the bottom front out toward the driver's side & while doing that pull from the back of the unit toward the back of the car & it comes right out! Screwing around with pushing in on the detents just tries your patience & will probably cause them to break. Anyway mission accomplished & thanks for your help!!!

amx1397

I would suggest you look on ebay and see if you can find one with the same number,this way you have your stock one, in case the tuned one does not work.
I changed my rear ratio last week had my tuner, Eurocharged find ,tune and send to me the tcm, now when ever i want i can put back the 307 rear and my stock tcu, i have two Differentials and a tcu for each of them

now you know the rest of the story Jim

Stevant

What are your tuners doing to the TCU. Changing when she shifts? I have a heavily modded SL and curious what the benefit would be since there is no change in any of the gearing itself. Insight please!

RAWAMG

Improvements Include:
- Modification of Torque Management Settings
- Full "M" manual mode and "S" summer mode.
- Reduced Slippage
- Faster Shifting
- Raised RPM Limiter
- Gears hold when in manual mod
- Raised Torque Limiters

kingnash

can someone post a pic of there the tcu is? i opened up the passenger footwell and i believe i saw a bass bose subwoofer.

kingnash

http://www.renntechmercedes.com/www/...moval_R230.pdf

cnterline

Get a used tcu ,make sure it has exact same numbers as yours,make sure it works in your car then send that one to get tuned ,you can find them on ebay,this way you have your original,the first one I sent out came back and my car wouldn't start with it,thank god I had my original to put back in. I would have been real pissed without it.the second time it came back all was well

acmw

TCU are not vin/key coded? I can just replace the module and it will work ? or will it need to be married to the key fob / eis?

latemodel21

No, it is not vin or key coded, nor does it get married to your car. You can "just" replace it if it is "variant coded" for your car ... example, an e55 TCU may have the same part number, but in order to use it in your sl55, you would have to change the variant coding to that of your SL55. As an example, I removed the TCU from my 2003 SL55 (which only allowed steering wheel button shifting in "Manual" mode as all 2003 SL55s and E55s did) and replaced it with what I thought was a 2004 SL55 TCU (had same part number as 2004 sl55 tcu which turned out to be common with other models including the 2004 E55). The TCU seemed to work for a quarter mile or so and then would go to limp mode (giving a code for incorrect gear ratio) ... so I checked the TCU coding (in the "control unit log") and found that it was "AM71" I changed it to "AM72" and it worked fine (and has continued to work fine for 6 years since). I think that "devoloper mode" is required to make this change . Worth mentioning, I did not guess at the "AM72" I got that from another SL55 (2004) ... my 2003 TCU that I removed was coded quite differently (something like "AM61" IIRC).

on a related note, Mercedes says that when switching from a 2003 to 2004 TCU (in an SL55 and E55), you MUST also change the valve body (to that of a 2004+) . There are folks on the forum who say they have made this swap without changing the valve body with zero issues ... I can't confirm that as I swapped my valvebody to a newer "blue top" solinoid equipped unit frm a 2004 E55.

Hope that helps,
Chris