Check Engine Electronics

richunters · #1 02-17-2003, 02:45 PM

In the two months that I owned my 98 E300D, the dreaded Check Engine Electronics message has came on twice. Yea, I know, most of the time it means bad MAS unit. In each case, I took an wait and see attitude as engine performance appear unchanged. In each case, the message went away on its own after about a week. I also noticed both times the light came on as I was running errands and having to shut off engine then re-start after driving short distances.

My questions are (1) If the light came on due to system detecting a temporary irregularity, is it supposed to shut itself off after a certain number of days or certain number of re-starts? (2) Do I need to take my car in - the next time message light comes on?

aTOMic · #2 02-17-2003, 03:06 PM

Take it to AutoZone for a quick, free diagnosis. they may say they can't read a Mercedes but you need to invoke the secret word "O B D 2" and they will be surprised that they CAN do it.

RE your questions, 1.) I dunno; 2.) the car stores the fault codes so it should not matter if the light is on or not.

HTH

-Tom

richunters · #3 02-17-2003, 06:47 PM

Thanks for the Autozone suggestion. But are you saying the car stores all the past fault codes, so even if the fault condition went away, the code history can still be read?

aTOMic · #4 02-17-2003, 07:10 PM

Yup. Do a search on "fault codes" or "OBD2" or just "OBD" plenty of good info.

blackmercedes · #5 02-17-2003, 07:18 PM

Maybe low voltage readings. Original battery?

Benzmac · #6 02-17-2003, 08:22 PM

The biggest thing to check is the fuel cap. You should just go ahead and replace it with a new OE!!! CAp.

You have to use and original cap!

JimF · #7 02-18-2003, 11:28 AM

after they are erased! Once they are erased, they are gone!

Regarding CE going off by itself: For my car ('94 S500 and I suspect for yours), the rationale goes like this for the DIAGNOSTIC MODULE (N59) [yes, I know you do not have a DM]:

If a system malfunction occurs, the diagnostic module receives a malfunction code signal from the appropriate ECU. If the same malfunction code occurs during TWO (2) consecutive trips, the CHECK ENGINE light is illuminated and remains lit until the malfunction is illuminated and the DTC reset.

For some DTCs, the CE can go off if the same error does not appear for "X" trips. X is different for different malfunctions. A TRIP is defined as "engine temp above 80C, car moving for 5 minutes at more than 15mph" and a few other things I've forgotten.

But you get the idea. You can drive the car and if the error was a 'glitch', the CE light will reset itself. In my experience this does not happen often.

richunters · #8 02-18-2003, 02:19 PM

Let's see, go to Autozone, check codes, check original battery, go to dealer's buy gas cap. Will do and thanks guys.

Crossing my fingers hoping for no more CE lights...

aTOMic · #9 02-18-2003, 02:47 PM

I thought the codes remained until reset by a scan tool; that is, even if the malfunction that caused the CEL corrected itself the code reader would show it. I may have been misinformed and I humbly bow to JimF's superior knowledge. I guess if I could choose anyone to catch my mistakes regarding CELs, JimF is the one I'd pick! Jim, your site is outstanding and I used it to learn a great deal about scan tools and MB electronics. In case anyone has not seen JimF's excellent site here is the link.

-Tom

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