Carsoft diagnostics - Serial cable connection - Mercedes-Benz Forum

LinkBack Thread Tools Display Modes
post #1 of 4 (permalink) Old 09-15-2013, 06:17 AM Thread Starter
BenzWorld Newbie
Date registered: Sep 2013
Vehicle: W202
Location: France
Posts: 2
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
(Thread Starter)
Carsoft diagnostics - Serial cable connection


I've already posted this yesterday in the audio and telematics forum but then I noticed that a lot of posts in that forum don't get many replies. It seems this general forum is a place to post anything so I'll try here instead. Apologies if repeating myself is considered to be not good form.

I'm trying to scan an old W202.

I have the carsoft 7.4 software that came with a 38 pin connector cable that I bought. The software installs and works fine.

However the connector was 38 pin to USB which I have since found out is useless with carsoft........ carsoft needs a real hardware serial port as has already been talked about in plenty of other threads.

So I've found an old computer with a serial port and I've bought a DB9 serial connector.

The 38 pin connector is one of the cheap ones with only 3 wires inside.

My plan is to solder the 3 wires to the correct pins on the back of the DB9 serial connector and then it should work right? I will have basically made my own 38 pin to serial cable.

I have the complete pinouts for the 38 pin side and I understand that the three wires connected to the pins are as follows:

Pin 1: Ground (Earth)
Pin 3: Power
Pin 4: Engine data

My problem is I can't find any information about which pins they should go to at the serial DB9 end?

The best I have at the moment for the serial connector is:

5: Ground?
2: Data in?

Not sure if a serial connector needs power at all?

So quite simply..... does anyone know for sure which wire goes where?

In addition, every combination I've tried so far has just given me "wrong communication error".
So does anyone know any reason why this woudn't work even if I had the wiring to the correct pins?

charlie pa is offline  
Sponsored Links
post #2 of 4 (permalink) Old 09-21-2013, 04:11 AM
BenzWorld Junior Member
Date registered: Sep 2009
Vehicle: Mercedes E220CDI /2000
Location: Copenhagen, Denmark
Posts: 5
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
38pin connector

Sorry, that will not work for You.
First, the communication on the 38pin connector is bidirectional 0-5 volt signal, the RS232 serial port on PC is receive and transmit on separate pins, +/- 3-12 volt.
I have tried to build a simple converter for this, but never got the software to Work with it. I ended up buying a carsoft box on Ebay, with cables, box and software. The expense was well earned back, as older Mercers are susceptible for all kinds of Wear outs in cables, connector, vacuum tube hoses etc. Spareparts are on the other hand available at fairprices, as long as You know what to replace.

dieselsmoker is offline  
post #3 of 4 (permalink) Old 10-06-2013, 01:56 PM
BenzWorld Member
Date registered: May 2012
Vehicle: 2002 C240 Auto (Hijacked by criminals)
Location: South Africa
Posts: 197
Mentioned: 2 Post(s)
Quoted: 0 Post(s)
Google "RS232 pinouts". In most cases you will use only pins 2 and 3 for data and 5 for ground for a standard DB9 connector.

ProvoZA is offline  
post #4 of 4 (permalink) Old 10-08-2013, 02:42 AM
BenzWorld Junior Member
Date registered: Sep 2009
Vehicle: Mercedes E220CDI /2000
Location: Copenhagen, Denmark
Posts: 5
Mentioned: 0 Post(s)
Quoted: 0 Post(s)

You can also google and find the pinouts for the 38 pin connector.

But it is not possible to just wire RS232 transmiit and receive directly together, and then connect to pin on the correct 38pin connector pin, as signal levels are not compatible.
The reason for the need of a real serial port on the PC is that carsoft is programming directly to the UART chip, because the protocol is non standard for a PC. However, even though I tried to build a levelconverter for the interface, I never got it to work. Could be something simple like I used too long cables or so, but could also be that there is some intelligens in the Carsoft box, that is needed for the communication to work. After some hours of testing I decided to buy the box. And it contains several chips, not just a level converter.

dieselsmoker is offline  
Sponsored Links

  Mercedes-Benz Forum > General Mercedes-Benz Forums > General Mercedes-Benz

Quick Reply

Register Now

In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Title goes here

video goes here
description goes here. Read Full Story
For the best viewing experience please update your browser to Google Chrome