Hi
My CEL came on on my 91 300SEL. Engine runs fine, everything seems ok. But the light stays lit.

So I did a search and found that I needed a LED. I bought one. Really dirt cheap, around $1.30.

So I open the hood, and find a 16 pin connector on the passenger side, under a cover that also goes around the hood light switch. Well, this 16 pin plug does not look like anything described in any of the posts my search pulled it. In my case, there is a push button at socket 2 and a light at socket 4. So I figured, ok, I'll turn the key on and press the button. The light comes on after a few seconds, but simply stays on until I released the button, then turns back off. I believe I used the connector once to find and clear soft-top faults, but I used the soft top button to read the codes.

OK, so I figure this must be for something else. I find another multipin connector next to the ignition module under another cover on the driver's side. This is a sort-of round plug, with 9 sockets.

Can somebody please tell me how to use these to pull codes and erase codes? Or at least direct me to what I should search for? The only ones I found were for the many-pin round connector for later model cars (I have a Snap-On graphing scanner I can use on those), or for a 16 pin, but where sockets 2 and 4 are available for the led and the shorting wire.

Help! Thanks in advance.

__________________
Thank You!
Fred
2009 ML350
2004 SL600
2004 SL500
1996 SL600
2002 SLK32
2005 CLK320 cabrio
2003 ML350
1997 C280 Sport

If you push the button too long or let go too soon, it won't give you any codes. I think I usually count to 3 or 4 and then let go.

__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

Thanks Larry! That worked.

Came up code 11. Air injection circuit short or open.

Well, ya, of course! I changed the air pump, but disconnected the clutch because I also ruined the hose between the air pump and check valve when I changed the pump out.

So now I have another question. Does the button test all system?

Or do I have to do the LED / shorting wire process to discover other faults in other systems using the other 14 test points?

__________________
Thank You!
Fred
2009 ML350
2004 SL600
2004 SL500
1996 SL600
2002 SLK32
2005 CLK320 cabrio
2003 ML350
1997 C280 Sport

The built-in led/sw only accesses codes from the DM module [ Emmissions N/59 module]
All the Engine Mangement and running codes codes are gotten from the other pins. You just make a led tool that duplicates the built-in one.

http://members.aol.com/ajdalton7/ledtool.jpg

Thanks!

__________________
Thank You!
Fred
2009 ML350
2004 SL600
2004 SL500
1996 SL600
2002 SLK32
2005 CLK320 cabrio
2003 ML350
1997 C280 Sport