1992 500E Check Engine Light on, but no code?
 

This is my 3rd W124 and I've always been able to get a code form the 8 pin connector (right side of car) with the LED. This car is not returning one.

1992 500E. 140,000 miles. Runs fine, although a little (just a tiny bit) rough since the light came on. It light after being parked at work for the day. I can't think of any event/incident that occured related to light. It just appeard.

What I have done:

- turned on ignition, engine NOT running, held down button in 8-pin connector for 3 seconds. LED on solid while holding down button. Released. Nothing (not even the single blink saying it's alive).

Cycled ignition and did it againg for 5 seconds. No acknowlege blink.

Cycled ignition once more time, held for 10 seconds (or more) and released. No blink. Turned off ignition for 1 min. Turned on. Waited at least 10 seconds and restarted. CEL still lit.

I'm perplexed. If I could read a code then I'd have something to go on here.. but.. nada. My local mechanic (who is almost 100 driving miles away.. not very local huh) said to check some fuses external from the fuse box, typically located near the battery. I found a pair of 5 ones in a seperate snap-top box but both are fine.

Totally at a loss here. I'd like to get the CEL to go away.. far far away.. but I'd also like to find out why it came on in the first place. Do I need to abandon my simplistic method of holding down the light in that 8-pin connector block and build one of Jim's RS scan projects and start plugging it into various combinations of the X11/?? connector?

HELP!?

PS. I've spend the last 3 hours looking at threads back to 2004 and so far.. nothing about a DTC that does have a working LED but does not serve up any code.. :(

The computer connected to the LED isn't responding...otherwise you would get 1 blink that means NO codes.

You need to have someone with dedicated MB scanner have a go..

That computer in is the box under hood & should be marked CARB.

Thanks Doc. I have a couple of other issues (such as the trans started leaking pretty bad about 2 weeks after I had it re-paired to fix blown reverse piston seal). I guess I need to bite the bullet and drive it or have it towned out there to get the leak fixed and have them diagnose the CEL. Ugh. I like to do this stuff myself but tossing parts blindly at a problem is not my idea of satisfying.

Thanks for the feedback.

- David

WOO HOO!!

The RadioShack code reader (kit and showband review) did the trick.

I was able to read a bunch of codes off of PIN 19.

2,4,5,6,9

When I turned the car on again, it only returned 2,6,9. Those three I actually had to clear using your instructions. I wonder which one caused the other faults.

Light is now OFF!!

The little reader is going to go into the owner manual book for use whenever the light comes on again (it would be great if it did not!).

Jeez this place rocks. Now if only the code reader would be able to stop the front trans seal leak I'm dealing with now.. :(