Blacknacoustic

So I bought a 03 C320 stuck in limp mode and won't get out of first gear and havent been able to fix it because the OBD2 sensor wouldn't power on. The battery is draining as well and I have to jump start it if I havent started it in a day. I've narrowed it down with some investigative work and this is what i've found so far.

I pulled out the entire ECU to check it, had two bent pins that I fixed back and checked the OBD2 sensor again with no results.
Checked the continuity of the OBD2 pins. 7 and 8 had 12 volts, but 16 did not.
So i'm currently trying to check the resistance/continuity from the DLC to the SAM module pin 11.

Unfortunately i have limited knowledge of these vehicles electrical systems and not sure where pin 11 is located in the SAM module.
Can anyone give me any additional information on where to look and a SAM diagram that could possibly break it down?

tjts1

Sounds like someone has monkeyed around with it before. Disconect the battery for 5 minutes then reconnect it. Sometimes that's all it takes. The fast drain is likely the power seat modules. Disconnect the power supply from the seats and see if it still drains. There's a quick and dirty $5 fix for this common problem.

Limp home mode could be ATF contamination in the TCM. Pull up the passenger side carpet and check the TCM for ATF.

Blacknacoustic

So there was water in the passenger side of the vehicle when i got it. I drained the water and took the entire power seat module out, so it isin't connected right now. My car is still stuck in limp mode.

tjts1

Then it's very likely that the TCM is water damaged. It can be replaced, it's not coded to the car. Find one with identical PN. You'll still need to hook it up to a scan tool to clear codes. Water damage would also explain OBD2 OBD2 not functioning. With water in the wiring harness you're in uncharged territory. Good luck.

Blacknacoustic

To be honest it sounds like it could be the TCM. are they any guides on how to replace it, and where's the best place to purchase one? Also the water was only located in the passenger front and back seat, not anywhere else in the car. Do you think if i change the TCM it could fix the issues. Also in checking the ODB everything is getting power but only pin 16 isin't. Could that be the same issue?

C230 Sport Coup

Make sure the car is out of the rain, and can dry out completely.
Water plays havoc with these cars...mine has died twice
from water getting in after rain. I'm quite surprised I haven't had any trouble recently
as here in NorCal it's been raining off an on for going into the 3rd week straight.
Very happy it hasn't!
Wiring diagrams are available on WIS and hacked copies are available on Ebay and or the
W203 Service DVD. Service DVD used to be sold by Mercedes directly from
their literature dept.
It was originally designed to work on XP and was ok on Win 7,
BUT I recently switched to Windows 10 64 bit and found instructions to get
it working, but haven't been successful in getting the wiring diagrams to work.
I posted on this recently, just look in my profile at my recent posts.

And as mentioned or not, TCM is under the right side footwell, super easy to access.
And yeah, easy to get a replacement on ebay, and thankfully not expensive.
As mentioned just match the pn exactly!!!
Hard to troubleshoot with a deal OBD port!
Im assuming if it has voltage the fuse is ok, but in case you didn't know, it has it's own fuse.

Blacknacoustic

Thanks for all the information on this, i ordered one today and hopefully it will be here before the weekend is over and i can get it in and see if it works. I bought some metal and terminal cleaner as well so wish me luck.

Blacknacoustic

Thank you guys!!!! You've been life savers. I popped it in there tonight and the car switched gears perfectly!!

jaGTAR KAHLON

Start with the basics. Check all fuses. Get a battery that works. 12v isn’t enough, you also need amperage. Check for a draw with an amp meter. You need a scan tool capable of accessing the body modules (Sam) and/or tcm to reset limp mode. Disconnecting the battery won’t work. There are connectors (forgot what they’re called) that you can access under the interior trim. Theyre for checking can bus communication . If you seen water. Pull all the relays and fuses out in rear and front sam, I’ll bet anything they are corroded. You need schematics, you can get WIS for 10 bucks on eBay and a bi direction scan tool for around 200. You can bypass the power issues by pulling the power wire from DLC and clipping it to another power source.

ah damn too late sorry

C230 Sport Coup

Glad to hear. Is the OBD port working now? Like I said, there's a fuse. Fuse chart is around here somewhere.
3 fuse boxes.

Blacknacoustic

So the OBD port is still not working, i don't think its a fuse but i think it might be the Sam console. im going to replace the entire thing and work my way down from there.