Where is my ECU?

[M Paul Lloyd]

Hi all, Sorry to butt in but... when I bought my W202 Class many an 'expert' was on hand to dish out dire warnings of horrendous repair bill's cost of this that and t'other that would have me regretting it sooner rather than later. Fact is, eighteen months later and it has cost me less to look after than any car I have ever owned.
Anyway, I digress, chief amongst these 'dire' warnings was failure of the 'ECU' without which my car would not run properly and repair was not possible only complete replacement at horrendous cost etc etc.The Haynes Manual shows where it is located, under a plastic cover to the back of the engine bay, but I chose to leave well alone, it seemed like the sensible thing to do.
But, I got curious as to what this fabled 'ECU' looked like so I had a quick look (see picture) and well? Where is it? do I need one and why does 'everyone' seem to think that my car won't run without one??

 

[Aussie Nick]

I think your ECU is the object in the middle of the photo with the black sheathed cable leading from it.
Believe me the water in the engine compartment will do wonders for the ECU.
Keep it up and you will find out what the others have been complaining about first hand.

 

[bigasotonuk]

Hi,
As Aussie Nic says the item with the black sheathed cable going to it.
For your information,
The round item adjacent to your ECU is your diagnostic socket.
The rectangular box adjacent to the diagnostic socket, if you remove the cover you can put 12v into the cars electrical system if the battery ever goes flat (not to be used for jump starting).
The relay with the fuses in the top is your OVP Relay.
There should be a plastic cover over that whole area, if you did,nt remove it for the pic my advise would be get one to avoid any dampness getting into these electrics.

 

[M Paul Lloyd]

Thanks for the info', consider it covered.

It was when I say the big empty metal chassis at the back I thought WHA?! but I see it now.
I'm not very good with electronics.

 

[Cosworth]

Take the windscreen washer bottle out, its under there.

 

[Cosworth]

have a look

 

[M Paul Lloyd]

Hi Cosworth, Thanks for that, now that is interesting, no mention of anything like that in Haynes, Lol.
It seems a strange place to put something so vital given how easy it is to spill windscreen washer fluid!!
I will exercise extreme care when doing so in future.
What other surprises are lurking in hidden corners I wonder?

Does anyone know what that big empty chassis at the back is for by the way?

 

[bigasotonuk]

Hi,
It was only the early models had it under the washer bottle, if you look under your washer bottle there should,nt be anything there.

 

[M Paul Lloyd]

Hmmm, Mine is a 95 reg' so I guess that counts as 'early' ??

 

[Cosworth]

Hmmm, Mine is a 95 reg' so I guess that counts as 'early' ??

Yes, so your car will have the ecu under the washer bottle.

Remember, always have a good battery in your car as I have heard of many cases where the unit blows with weak batteries and when people try to jump start.

 

[bigasotonuk]

Hi,
The ECU is located according to the type of fuel injection system on the car, P.M.S. or H.F.M.
The unit under the washer bottle is known as the P.M.S. module.

 

[azali]

info pls on pms

The PMS unit has a vacuum input just like the one in the pic. I wonder if PMS from W202 and E200 is interchangeable as I need to find one myself (for my E200).

Mercedes equipped with PMS are (plucked from the internet):

Manufacturer Type Model Engine
Mercedes C180 93- 1.8
Mercedes C200 93- 2.0
Mercedes E180 93- 1.8
Mercedes E200 93- 2.0

Are the PMS units for these cars interchangeable?
Mine is:
015 545 26 32
siemens

vin:WDB12401928946044

 

[Bolide]

The unit under the cover by the empty rack is the ABS ECU. That's a pretty standard thing you'll find on most Mercedes since since about 1987

Nick Froome
www.w124.co.uk

 

[M Paul Lloyd]

Yes, so your car will have the ecu under the washer bottle.

Remember, always have a good battery in your car as I have heard of many cases where the unit blows with weak batteries and when people try to jump start.

Thanks for that Cosworth, I will bear it in mind, I had planned on replacing the battery later this year but may do so a bit sooner. I seem to recall being told that jump starting these electronic boxes is not a good idea. Lets hope it never comes to that?