No ECU after flat battery

[lordgaz]

Hi All - Our S320 3.2 petrol 2002 went off for some new parts at the local garage.. It was there a while, and when we picked it up, the battery was only just strong enough to start it.
At home, it sat for a while (3rd utility car) and the battery was totally flat when I came to start it.
To get into the boot, I applied power over the front 40A fuse in the front right (drivers side) fuse box and earth and boot was able to be accessed (adding a new battery as the old one would not hold charge) - However, when I tried to start the car with the fresh battery, nothing happened (except for the fan spinning wildly) - Further investigation with a diagnostic scanner (MB-2) shows it cannot connect to the ECU -
Could I have disturbed a connection in the fuse box (I did at first unclip the fuse carrier from the zinc clip at the front of the box when I was trying to find a positive+ power point which was before I read about using the 40A front fuse) - Where is the ECU? is it on the same side as the fuses?
Bit worried - think I may have fried something? or hopefully disturbed an important connection on the fuse carrier? -

 

[lordgaz]

Oh dear - checked the ECU, and when I pulled a connector, water came out with it - Removed all connectors and opened the ECU to find this horror. Looks done for, but I will dry off and clean up and see what happens

 

[EmilysDad]

Oh dear! I hope you get sorted & it's not too hard on your wallet

 

[Blobcat]

That's not good, looking at the leaves in your first picture immediately made me think of water damage somewhere.

I'd try and dry it out, however I expect corrosion damage under the chips as the legs are so close together which means it could be unreliable in the future. Having said that, you've nothing to lose by drying it out cleaning up all that you can. Liberal amounts of contact cleaning lubricant and see how it goes.

 

[lordgaz]

Yes, this is all my fault, and it happened I think during the perfect storm of me opening the bonnet and fuse box lid on Wednesday to get the boot opened (as previously mentioned) and not putting the lid back on the fuse box (though I did close the bonnet), massive downpour Wednesday night and all Thursday - Discovered problem today. Either that, or water has been building up over time somehow in the bottom of the fuse box - Anyway, I dried out the ECU, and used some PCB cleaner, and it is definitely fried.
I am going to get a second hand one from Ebay, and swap over the "VIN lock" chip.. That should be fun

 

[bembo449]

did you try the bag of dry rice trick ? fixed many a water problem using that method pal

 

[Botus]

circuit board on bottom left side of picture is very bad

 

[lordgaz]

circuit board on bottom left side of picture is very bad

Yes, it is dead. I'll post an update once I have my donor ECU delivered and I have swapped over the Vin code chip (with some photos) - Fingers crossed..

 

[lordgaz]

OK - Problem has now been solved - I bought a 2nd hand ECU with matching part number, software version and Q number (not sure if the last 2 specifics are important or not) - The ECU does not need to come from the exact same model of car I believe - just match the numbers.


I opened up both old and new ECU's and located the chip which needs removal - (shown circled) and marked the old board with sharpie - I also added a very small dot of nail varnish to the top edge of the chip I wanted to remove with a pin - This helps to keep track of which is old chip and which is new chip (in case of sudden gust of wind or something - it also helps when fixing the chip onto the new circuit board to ensure it is the right way up!)


You need to remove the circuit boards from the metal housing - Some mild heat may be necessary to soften the sealant holding the back plate onto the circuit board.

Next - I cut out some kitchen foil peices with a chip sized hole in them to act as a heat shield - I used 3 layers.

Then, I heated both boards in the oven to 100 degrees c just to help prevent shocking the boards when I used the heat gun - I put both in with the oven cold, and let it get to temperature - then removed.

On a flat surface I then added the heat shields and used a hot air gun set at 365 degrees and wafted this over the chip pins on the "new" ECU VIN chip, going round the chip for about 10 seconds while holding the chip with tweezers - once free of the board, discard this chip.


Returning to the cars original board, I removed the same chip and kept it safe.

On the "new" circuit board, I cleaned the 8 tracks where the chip pins go with a quick run over each one with a soldering iron, then carefully placed the chip I had been keeping safe onto the board, and held in position with tweezers while I fixed each chip pin to the board with a soldering iron.


Allow to cool, reassemble into the metal housing, and refit (with the car battery disconnected) - and as if by magic I have a car which starts again for the princely sum of £33 in parts - and not some horrendous invoice from a specialist!

 

[Larkone]

Respect on that repair

 

[M80]

There was me thinking you would be changing barrels and locks as a matching kit.
Well done that man, you're braver than I, and far more knowlegable.

 

[lordgaz]

There was me thinking you would be changing barrels and locks as a matching kit.
Well done that man, you're braver than I, and far more knowlegable.

Not so much brave, but nothing to lose in real terms - The ECU was shot, and I figured a Merc or specialist replacement would cost more than the car was worth - The chip change avoids the need for complete change of barrels / key etc as it just clones the old ECU info onto the new one - It took about 10 mins to do (after a bit of research and lot of 'in head' planning)

 

[M80]

Is your SAM in the same enclosure, as mine is?
I've seen SAM's go down due to ingress, well doing strange things with lights and horn. But on oldish MB's they're just plug and play when a same SAM is sourced.

 

[Botus]

I bought a 2nd hand ECU with matching part number, software version and Q number (not sure if the last 2 specifics are important or not) - The ECU does not need to come from the exact same model of car I believe - just match the numbers.

surely must be a similar year and same engine or the map would be wrong.... they do use the same physical ecu on other stuff

my air-cooled two pot GS has the same ecu as the 4 pot LC K1300

 

[lordgaz]

surely must be a similar year and same engine or the map would be wrong.... they do use the same physical ecu on other stuff

my air-cooled two pot GS has the same ecu as the 4 pot LC K1300

Yes, I guess I could have been a bit clearer - in my instance, I needed to find a ECU with same part number from a similar V6 M112 engined merc - but I think it did not need to come from a W220 S-Class, - A W210 ECU with the same part number would be ok. And I would hazard a guess that any ECU I found with the same part number and version code would have worked without knowing what model the donor vehicle was (which was the case when I bought the replacement on Ebay - no mention of model it came from)

 

[Botus]

I'd expect maps to be reasonably different between models...

so an E class shouldn't be the same as a S for instance. of course with same engine will be similar, but exhaust, air box, gear ratios, compression, cams (possibly), and state of tune could be very different... ones pulling 500kg more lead for a start

and for tractors an S would tend to get a DPF before the earlier ones

 

[lordgaz]

From a little checking, I think ECU's with the same part numbers / codes from the below vehicles will all work

https://ecu.eu/mercedes/engine-control-unit/me2.8/mercedes-a1121530879-bosch-0261207573-104080.html

MERCEDES C240 (C-Klasse, 203) Year of manufacture 2001 Engine code 112.912
MERCEDES C240 T-Modell (C-Klasse, 203) Engine code 112.912
MERCEDES C320 (C-Klasse, 203) Year of manufacture 2001 Engine code 112.946
MERCEDES C320 T-Modell (C-Klasse, 203) Year of manufacture 2001 Engine code 112.946
MERCEDES CLK320 (CLK-Klasse, 208) Year of manufacture 1997 - 2001 Engine code 112.940 TCU code 112.940
MERCEDES E240 (E-Klasse, 210) Year of manufacture 2001 Engine code 112.914
MERCEDES ML320 (M-Klasse, 163) Year of manufacture 2002 Engine code 112.942 TCU code 112.942
MERCEDES S280 (S-Klasse, 220) Year of manufacture 1999 - 2002 Engine code 112.922 TCU code 112.922
MERCEDES S320 (S-Klasse, 220) Engine code 112.944 TCU code 112.944

 

[lordgaz]

I'd expect maps to be reasonably different between models...

so an e class shouldn't be the same as a S for instance. of course with same engine will be similar, but exhaust, cams (possibly), air box, gear ratios and state of tune could be very different... ones pulling 500kg more lead for a start

You're probably right - I've only started the car so far, and not driven it! I'll let you know if it goes like a rocket or a snail!

 

[Botus]

isn't the map part of the part number?

one on the right says FD 01M10 the left is FD01M09
wonder what that means? is the right a year newer... with those part numbers I'd think its the right one....

 

[Kev555]

Map is usually stored in the main chip if I remember right, ( had a guy clone a an ECU for a burnt board in a vehicle I had a few years back, just removed the chip and soldered it into another board which saved me a small fortune). Possibly just a matter of removing that chip and putting it on your board if you have any issues