CraigG

Hello everyone, I'm Craig...

Just a quick question, I've had a bit of an issue with my car, and I need a new engine ECU. I've found an ECU from a 2012 coupé, but my car is a 2009 saloon. I've been told that the newer ECU isn't compatible with my car due to a torque splitter or something? Is this true, or will the ECU from the 2012 be ok in mine once it's been programmed? I'm just exploring options, as I don't really want to fork out nearly £2k on a new unit.

Thanks in advance guys!

abcut973

That is a good question. All ECUs are vin coded to their specific car. But some tuner can clone your OEM onto another one. I don't know about the compatibility between the models though. Common sense would tell me that yes. Because as far as i know an ECU is just some kind of computer being coded. So the only difference I would see is hardware.
Pre-FL and FL have the same M156 engine, different transmission but they have their own TCU. I would say call weistec they might be able to confirm.
Now what is your problem with your ECU? If it is corrupted the only way you can fix it is to go to the dealership. Unless you have your OEM file backed up somewhere
GL

CraigG

I bought my car with a full main dealer history, but the auxiliary belt went on it 6 weeks later. The garage I bought the car off have since stated they sold me the car with no warranty, but have gave me some money towards fixing the car.

The problem is, when the belt has shredded, it's cut into the loom, wires have touched an we think the ECU has shorted. The problem I've got is an intermittent starting fault. Sometimes the car will start with no problems, and run a little bit rough, and most of the time it takes 2-3 cranks to start it. The CEL is on and the cam position sensors, crank sensor and fuel pressure sensor(?) are all only getting 3v. All the sensors have been changed and there is continuity throughout the loom, so it all points back to the ECU, as this is where it's earthed from, am I right?

abcut973

Yes the ECU is the center command but if it is shorted than nothing on the car will work. You won't be able to crank it up.
Your problem sounds more like a misfire. What code did you pull?
Did you guys already investigate that way?

CraigG

It's not a misfire, it's just that all of the sensors are only getting 3v. I haven't got the codes to hand, there was 12 faults. They came back to low voltage to the sensors. All the sensors have been replaced at a cost of £600 up to now, and it's still the same. The loom has been checked for continuity after it's been repaired, and that's all perfect. Relays have been changed, so the only thing left is the ECU, isn't it?

Cheers for the help by the way, it's massively appreciated!

abcut973

Ok well I never experienced that fault so I don't know what could be wrong there. You guys checked the fuse for this sensors?
For sure the ECU is linked to all those sensors but it just takes inputs from those sensors. So if the car doesn't start it is because the inputs for ignition doesn't meet the criteria therefore the ECU does nothing .
Like I said earlier if the ECU is faulty then nothing should work. You shouldn't be able to start the car I think.
How about you change the wiring harness that has been damaged?

CraigG

The car doesn't start though, not all the time, it just cranks... But then it'll start every now and then? The faults are down to voltage at the sensors, like an earthing problem... The harness is fine on all the continuity tests. The loom never actually split, the outer was just spliced and a few wires touched.

Has anyone had the belt go and cause problems?

CraigG

I'm really starting to regret buying this car, and a C63 experience shouldn't be like this!

m a x i m u s

Sorry to hear about your issue, that's terrible. Not a car electronics expert here, but like stated previously, if the ECU is toast, I would think the car wouldn't crank at all. Maybe this is a separate problem unrelated to the whole belt shredding thing. I would replace all the wires, etc. that were damaged and check connections. And maybe have your battery tested?

CraigG

Apparently, it's just a small part of the ECU that's damaged. The car starts (sometimes), runs and drives... I've been investigating this myself with a few auto sparks, and they've all said the same thing, new ECU...

m a x i m u s

Is there somewhere you can send the ecu to have it tested? Could save you $$ if the ecu checks out.

CraigG

Yeah, I've sent it off, they've tested it and sent me a new ECU, but that never worked at all, when we plugged that one in, it came up with "Internal error". They did say there was a fault on my ECU, but 'apparently' Mercedes ECU's are impossible to get into, due to immobilisers etc. So I've been told the only way to go is to get an ECU from around the same year, or get a virgin ECU. So far I've found an ECU from a 2013 car, for really cheap, but not cheap enough for me to buy it and just discard it if it doesn't work.

m a x i m u s

Oh, I see. Sounds like then for sure at least your ECU is bad. Have you checked ebay or parts yards? Also, maybe contact a tuner like Weistec or Eurocharged; they may or may not have ECU's lying around, but it's worth a call or email. I thought I needed a new intake mani, and was gonna get one from Weistec (I know it's not quite the same situation since they swap mani's with the superchargers all the time) but I ended up not needing one after all.

CraigG

That's what I'm hoping to be honest, I've contacted Weistec, but that's it. In the UK, there's not really that many tuners, so it's all oversees companies.

Merc63

I have two ecus collecting dust. From a 2009 c63.


You will need a tuner to copy your file onto the used (new) ecu I think.

roadtalontsi

mb ecu's are pretty durable to shorts, Im betting the engine harness repairs are not up to par. Without some aftermarket tuner to copy your vin and file onto any used ecu is a paper weight. The dealers get one chance to mate the ecu to 1 vin and thats all when they are new.

CraigG

Does the ECU need to be virginised? Is that correct?

My mechanical knowledge isn't fantastic... Human body knowledge is fantastic... If my car was a person, I would have fixed it myself by now!