where exactly to read fault codes?
 

I read that other members seem to have an LED system for reading engine fault codes on their w124's.. apparently, this is somewhere on the passenger side near the battery.

I can't figure out exactly where this is supposed to be. The closest thing I found is highlighted in red, but there is no LED / pushbutton. Is this the right spot to look? Mine is a '93 300CE, does it not have the LED pushbutton system?

picture attached.

That is the correct connector, and here's where I was told to get the codes:
http://www.peachparts.com/shopforum/tech-help/107630-e320-16-pin-dtc-charts-inc-pin-8-pin-14-a.html

thanks for that link, I actually have it bookmarked from my researching on this! :)

but, am I supposed to have a built in MB LED / pushbutton for basic diagnosis? I'm under the impression that some w124's have this.

You need to build the code reader to read all the codes anyway. It doesn't really matter a lot whether you have the built in LED/pushbutton.

I've recently been through this learning curve.

The built-in pushbutton only reads emissions (CEL) codes, there are many codes on pins 8 and 16 that are critical and will not read from the built-in button and LED.

I built the box, using around $10-$20 of new parts from Radio shack (12v LED assembly, pushbutton, banana plugs, small plastic box) in around 30minutes and it is well worthwhile IMO. Doesn't tell you everything, but it helps.

<The built-in pushbutton only reads emissions (CEL) codes, there are many codes on pins 8 and 16 that are critical and will not read from the built-in button and LED.
>

No codes on pin 16...pin 16 is Pos+ 12v to power the tool.
The pins are 8 for HFM amd 14 for EA/CC module.

The confusion all are having on the PB is simply this:
If the Car is CAL Emmissions , it has a PB and a CE lamp.
If Not, it is Federal Emmisions.

Simple...No CE , NO PB

The car in question [ '93 300CE ] is Fed Emmissions and has neither PB or CE.

wow thanks that super clears it up! off to radioshack!