OBD1 Pin connections

Hi all,
I've put together a little serial code reader for my '89 300E that is running OK but not well... idle is rough.... and I 'will' track the problem
down. Which pins on my X11 socket that accesses the ECU will read the most important codes. Appreciate any help.
cheers, guenter
ps I know pin 3 displays the oxygen sensor for example
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Check your email for a diagram from the MB WIS software.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Perfect Doug, many thanks!
cheers, guenter
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Can you share some information about this code reader, or the pin assignment? I would like to know what my Check Engine light is trying to tell me. Thanks.
Guenter Scholz wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

the code reader is rather trivial. simply a momentary push button switch wired in series with an LED (+resistor if it's not internal to the LED). Then the other end of LED goes to batterie's +'ve and the other end of switch to battery's -'ve. The connection between LED and switch has a third connection added (either at LED or switch terminal) that will go to the pins of X12 connector (it has a plastic cap with the sockets for the wires) and is on secondary firwall near battery. Again, I know for certain this is the case for 88 and 89 W124's (103 engine) but not sure of other years. One then simply presses switch for a few seconds to activate ECU that then blinks the LED a number of times to spell out the difficulty it thinks exist. One blink means no problems. Moreover, you can then also erase any stored codes again.
I can send you more detailed information/pictures if you need
cheers, guenter

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.