My 95 e320 wagon's check engine light came on a while ago... Around the same time my built-in phone system (Benz part above the rearview mirror) started going wacky and sending me random messages and the antena would go up and down randomly. There is no phone in the car, although it had a factory phone installed in the armrest compartment.

I remove the phone system fuse near the battery that stopped the messages and the antena problems, however the car stared idling poorly when coming to stop or decelerating to go around a corner. The idle smoothes out again after about 10 second, and then the car runs perfect again. It doesn't always do it.

I made the code reader as described in the forum and pulled the following codes;
Pin 4 code 10
Pin 8 code 4, 13
Pin 14 code 11

The wiring harness looks poor around the temp sensor. It probably has not been replaced.

I realize I should replace the harness first, but since the car actually runs great except for the 10 seconds of poor idle when I come to a stop, maybe someone can tell me what I am facing based on the codes....

One other thing; the cruise control used to work perfect but it now is sporadic, sometimes it works, sometimes it doesn't.

Thanks in advance

Looks like Harness is suspect ..

BUT...............

Take the old OVP out and see if it is the original..there was a part# change
[ ARCHIEVES has that info] and if so, change it regardless..
Then charge the battery right up to full state and retry the car..

If still persist..Wire harness is just about had it...that is the most likely, but your complaints do fit OVP/Low Voltage ...so I would do that first.

I am assuming you did not go and get a code with your tool from Pin #4 as you state, but rather, you used the Factory DM SW/LED that is there ..correct?

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A Dalton

Ok, I'll check the OVP tonight.

No, I used the homemade tool. This is the same code (10) I get when I use the built-in PB and LED.

I see ..
Well, we do not seem to be on the same page on this..

Can you tell me HOW did you use the tool to go to PIN # 4 when pin #4 is the LED ???
Is this some kind of magic or something .......... ???

Pin 2 is the built-in sw and PIN 4 is the built-in LED on that chassis.

Maybe you are mistaken and you went into pin #3 ????
I very much doubt you went into pin #4 b/c there is no socket for tool insertion at that pin................
Please clarify how this can be done........

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A Dalton

Yes, you are correct I used the built-in LED for what I called pin 4. I used the homemade tool for pins 8 and 14.
When I read your original response I assumed the 'Factory DM SW/LED' was a special diagnostic tool (which I suppose it is)....
Rereading I see you meant the push button / LED.

Hopefully that puts back on the same page.

Very good.

The reason this is of importance and stood right out is b/c Euro exports to certain countries do not have the N59 Emmisions Diagnostic Module set-up for Legal Emmissions Mandates...so, you can see why the correct info is important to us making a diagnosis..we only have the info you supply......... if you had an open #4 socket, then my very first diagnostic thought is you do NOT have a CE/N59 equipped 124 chassis... when , in fact, you do.................which puts us back on the same page.

Regardless , my diagnosis/steps , although not complete yet, is still the same. I would start with OVP part# verification...........

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A Dalton

That makes sense.

I will check the OVP tonight, as well as make sure the battery is fully charged.

If the OVP is #000 540 52 45 I will buy the newer one.

I'll let you know what happens.

Very Good..

The OVP is suspect b/c on HFM/SFI full electronis systems , the OVP is the MAIN power feed for ALL Engine management .............

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A Dalton

Ok, so here's what happened...

I removed the nut/bolt combination from the OVP bracket and lifted the OVP out from behind the battery, I pulled the fuse out but it looked to be ok, so I put it back in. The part number was the new one 540 67 45. I gave it a couple of shakes and tapped it a few times for good measure and put it back in.

I also checked the battery, 12.7 not running, 14.18 running at idle.

I tried to reset the codes but only the pin 14 code 11 cleared completely and went to 1 flash. I could clear pin 8 code 4 for a few minutes but it came back on when rechecked. Pin 4 code 10, and Pin 8 code 13 never cleared at all.

But here is the amazing news! The check engine light is off, and the car runs great, no more idle problems.

So, the questions I have are;
Why is the check engine light not on if the codes are still set?
Should I replace the OVP now or wait until this or another problem occurs?
Any other suggestions on getting rid of the codes that are still set?

This excersize absolutely proves that one should not start replacing things without having a good idea as to what is really going on.

Thank you so much for your help!

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I notice you have the newer relay, so I would clear all codes and then see what comes back...
I think you are not clearing the codes correctly..after each code , you have to hold the button down for 8 sec , but you have to do that within 2-4 secs of retrieve, and it has to be done after each code , individually. You then have to turn key Off for 10 secs , On for 10 and then restsrt the car.
Do not expect a single flash from the DM b/c the car has to go thru all emmissions self tests before that can happen.

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A Dalton

Ok, I will try again. It could be I wasn't starting within the 2-4 seconds.

Driving to work today was great, the idle problem is 100% surely gone.

I will try to rest the codes again tonight and reply back then.

That may indicate the OVP pins were not making a good connection in their socket..common problem and one can usually tell by looking at the base of the OVP for discoloration on the pins and the base of OVP. Same goes for the fuse on top..

A crude but effective test is to tap the relay when the trouble arrises and see if one can see a difference in running, or if not starting, does a few taps get it to start..
If Yes..OVP replacement is usually the remedy...

Many Benz Techs carry a spare OVP in their toolbox to use as a diagnostic test tool b/c it is one of those faults that are easier to track down by popping in a Known Good part and see if that fixes the problem, vs chasing around for days with a Scope, etc.........
OVPs have such a reputation for faults that they get blamed for EVERYTHING, from causing Flat Tires to Streaked Windshields......

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A Dalton

Ok, so drving home the engine light came back on and it started stumbling again when I can to a stop, althought it seemed lke it happened less often then previously.

I got home and rechecked the codes. Pin 14 1 flash, so nothing new here, pin 8 - 4 & 13, and pin 4 - 10.

I reset pin 8 - 13 right away. code 4 would light almost a quick as I reset it. Finally I had everything clear. Is pin 4 supposed to flash once, like the others? Because it would either flash 10 or nothing.

Anyway I took it for a drive and the check engine light did not go back on, but I did have some idle problems, and when I got back the same 3 codes were back. Pin 8 code 4 & 13, and Pin 4 code.

Hmmmm... So, my first guess is the OVP is flakey and I should replace it. What do the other symtoms tell us?

Please stop calling it pin 4..there is NO pin 4 ..it is the DM.
And NO, the DM will not flash 1 like the PIN ONES do until the DM does a complete Emmissions self test.

Go here.
http://www.peachparts.com/shopforum/showthread.php?t=107630

I believe you could have a bad MAF sensor , bad wiring harness to it, or a bad feed from the OVP. You do not have the equipment to test these, so you may want someone to look at it or you may want to chance the OVP, although my first suspect with those codes would be the MAF sensor or wire harness..Archieve search it..sometimes the MAF can be cleaned and you can cut open the harness and take a peak. Harness short is suspect b/c you are getting immediate codes. While it is running, flex the harness and see if engine changes.

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A Dalton

Ok, thanks again for all your help.

Once I have a resolution I will post it.

Sorry about the pin4\DM thing. DM it is! ;-)