I know I could end up at the dealership with this, but I thought I'd try here. There is no shop near where I am this week that can read MB codes.

The check engine light on my "new" '91 190e 2.6 comes on after about two minutes of driving. The car runs fine, no symptoms I can identify except the light.

I attached two vacuum hoses that seemed to belong together but weren't. That didn't make any difference one way or the other. Afterwards I disconnected the battery for a while to reset the diagnostics, but that didn't change anything either.

Does this remind anyone of a problem you've heard of or experienced?

Thanks for any help you can give.

1-Turn your ignition on but don't start the engine (so that the warning lights light up).

2-Open the hood and take the lid off the box circled in the picture below.

3-Hold the button down for 2 seconds, and count the number of flashes by the LED.

4-Hold the button down for 6 seconds, the LED should stay lit for about 1 second (this indicates the code has been cleared).

5-Repeat steps 3 and 4 until all of the codes have been cleared. you'll know they've been cleared when you only get 1 flash from the LED.

6-Check the # flashes w/the codes at: this page, look under the m103 heading.

Attached Thumbnails

 

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1990 190e 2.6 - The only one I can really call "My Car".

1987 190e 2.3 - The donor car's up and running, only mods are Euros and a Sony headunit. My Dad's runabout now.

1990 300e 2.6 - The parents' ride.

That little box on my car doesn't have any buttons or LEDs, just a bunch of numbered holes...

It would have been cool if that had worked, though! Can I replace the one I've got with that kind of box...

MDB

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

build this if you'd like to read the codes. Plug the +/- to the battery and the other plug to pin 3. Then, with the ignition on (but not started) hold down the switch for 2-3 secs. Count the blinks (#=code), write down how many blinks, then repeat until you get the same number of blinks (you've gotten all the codes once you get the same number for the second time). Post the codes.

To reset the codes (and the CEL) after each code is displayed hold the switch down for 8-10 seconds. This will reset each code individually, if you have more than one code you'll need to do this after each code is read.

That worked great! Thanks for the schematic and instructions. I got the codes. Now on to the fixes..


MDB

So the fixes turn out to be things that can wait a day or two until I get home: O2 sensor and EGR valve. I could drive home to South Carolina. That is now done.

On the way, I stopped for gas once, and when I started again the car was running very rough, and it was hard to keep it from stalling. The light did not come on again for quite some time, and as long as the light was not on, I had this rough performance. When I got back up to highway speed, the light came on and the performance was smoother. Periodically along the way, the light would go out, and the car would balk at the accellerator. In a few minutes, it would come on and performance would improve. Then it came on and stayed on until I was home.

Anybody able to throw light on this behavior? Is the ECU failing? Thanks.