Well, I read your five, so here are the real ones , in order of operation

1- Engine vac is supplied to EGR SOV in front of engine [ white plastic line under front cover .very common EGR fault on 104]

2- SOV gets an electrical command sig from ECU, allowing vac to pass to EGR actuating Port. [ 12 volts to SOV to open SOV..not a common fault , but a sticky/dirty SOV could be the problem]

3- Vac diaphragm opens EGR valve, allowing some of the exhaust gases to flow thru EGR valve. [, this is where the hand vac test will verify the egr open/close operation to allow flow]

4- Exhaust gases are sucked back into engine via a connecting tube from EGR valve to engine head port.
[ this is where the hand vac will verify a blocked tube at idle..very common on 104, but often mis-diagnosed b/c everyone just jumps right to that conclusion..kinda the OVP scenerio of the EGR system]

5. The completed process creates a recirculated loop of the exhaust gases back thru the engine, where they started [ EGR= Exhaust Gas Recirculation ] If the ECU pressure monitor does not detect this change in pressure when EGR is activated, the Diagnostic Module N/59 triggers code 5, telling the owner he is polluting the Atmosphere and better do something to fix it or else !!!!!!
So, if all these seem OK and the system passes the hand vac test, the probale suspect is the common sticking of the EGR valve and the remedy is to upgrade it to the modified part.................or a bad pressure sensor.

__________________
A Dalton

Give me a little time on that one.. and I will jpg it over to my WEB page and post it back here for et al..........

I have it here somewhere, but I have stuff piled to the ceiling..

__________________
A Dalton

Mercedes Benz
Campaign # 95-0131

104 Engine w/HFM-SFI management systems
EGR part# 002-140-13-60

*note:

If your EGR valve has a red/white paint dot on top, it has already been updated by a Benz Dealer...when there is a Campaign, they do these when the car goes in for normal service, and not for an EGR complaint..so it is possible the car was done already without one even knowing it, as the part # did not change, just the shaft diameter was decreased for clearance problems .......[ the paint dot is just a way to signify upgrade for future Techs at the Dealership, confiming Campaign has been already been adressed]

__________________
A Dalton

Are these recall-type free repairs? I don't recall seeing a dot on mine.

__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

Campaigns are not recalls.
They are service changes that only get done as the Dealer is doing in warrantee normal service.

__________________
A Dalton

Day 5: And the Winner is....

Deanyel, for predicting Possibility Number 1 would the outcome!

Perhaps because I was in a dark corner of a basement parking garage when the CEL returned, it did indeed appear redder and brighter, as it glared and sneered at me... mockingly.

Now, on to the Arthur Dalton 5-step list....

__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black