Tried to read my codes today on my 88 w124. I have the 8-pin diagnostic port next to the battery. I hooked up the led and with key on engine off the led light flickers and then stays on. It should be off.
What does this mean and should I be concerned?

Somehow the test port is grounded. I guess I'll play around and see if I can figure it out.

that some model's LED is always on; it blinks "off".

Check it out: press it for 3 -5 secs and let go. If it blinks one (1) off, it's working AND theres no DTCs!!

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Regards . . . . JimF
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'94 S500 Cpe

Visit my Mercedes Web Page

Thanks Jim I'll give it a shot and let everyone know.

What's the status of the CEL? California or Federal car? How does the car run? Why are you running a diagnostic at the plug?

Peter

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Auto Zentral Ltd.

Everything is fine, its just I have an ASD light-on on the dash. I reset it and it came back a month later so something is up with the ASD. I am trying to read the code from the ASD pin on the board to tell me what it is thats all. I suspect the brake switch.