i wouldn't recommend it, you could fry the DME

 

Another update to this thrilling saga!

I got the car towed today to another shop that specializes more in Mercedes. The vast majority of their clients. The last shop didn't really make any progress last week beyond discovering a failing coolant temperature sensor causing the radiator fan to stay at full speed. Probably caused by the overheating and blown radiator incident.

Got back some decent data from the last shop too:

Codes pulled after overheating event prior to radiator / alternator work:












Blown radiator:







New Alternator test results:

 

-- We see a long list of STORED faults witnessing low voltage.

-- Yet there are NO significant ACTIVE fault.

-- Alternator voltage test does not look bad

ALT 14.4V output looks ok

I don't believe 3x ALT can be bad... the remote ECU control make them work poorly.

Your exploded radiator witnesses extreme heat caused by ECU likely soft-crashed.

Right now this wild chaos is centered around part of the ECU. It can run the engine and still disfunction by not running fan or sensing heat - It really possible the poor heat control is a telltale sign of bad cowell GND reference post -

(The last GND I have not yet cleaned up and I'm no stranger to W212 "heat + yoyo" much like here but smaller)


I would really go after cleaning the poor chassis GND factory-painted before replacing further parts. Inspect wet carpet...


chassis volts/amps
You have incentive to watch what your voltage is up to while driving.
I don't recommend jumping onto ALT-LIN right now while ECU is wild enough to blow-up radiator.

 

Apparently the alternator voltage is actually within an okay range now. Staying around 14V, but the alternator test is still failing. Current shop does not suspect any issues with the grounds. They inspected all the relevant grounds, but not sure exactly what all is included here. Public docs around ground locations seem iffy at best and I wonder how much they vary based on engine.

But yes the top suspect is the ECU at the moment. Currently waiting on the ECU and related modules to be updated via software. This was recommended by the current shop. Don't really have any hope this will make a difference but it won't hurt to get it done. Current shop also inspected the main harness connector going to the ECU and did not see any sign of oil. I do know I had oil in the harness, so I don't think it could be ruled out at this point, but current shop doesn't think it's likely.

I think I'm past the likely culprits at this point though.

 

wait so how did it suddenly just decide an alternator works now? I think the DME does control the alternator, so ecu is kinda on my radar now. I cannot believe HOW wrong I was about this car along with the rest of us in the beginning jesus

 

is there oil at the ecu pins?

When I tuned my e63, my tuner charged me $50 to clone my OEM/stock ecu to a new donor ecu off eBay and then tuned that donor ecu with the tune map etc. donor ecu's for $80-200 on eBay.

could be a quick way to determine if you just have a bad ecu if you're about to ditch the entire car over this


can the shop check your ground points?
https://mbworld.org/forums/coupe-roa...-stalling.html

 

I mentioned the current shop already checked the grounds and ecu connector. It was all very clean although I’m not sure what all grounds they checked.

Right now I’m waiting for them to update the ECU. If that doesn’t make any difference, I’m guessing we’ll try swapping the ECU.

I think it’s the labor that makes it a bit tricky rather than the parts.

 

So when will you call it?

 

What do you mean?

 

"Call it" as in "the fight is over, time to sell this car"

 

If it needs a new engine / rebuild. But I think the possibility of that has already been ruled out.

Although at this point I’m probably not too far off from the same cost of that. But the work I’ve done so far, should have my motor in a better condition that most other available.

I’m hoping that once I have this issue sorted, I’ll be set for the next 50k miles (or more?) or so aside from regular consumables.

 

ECU updates made no difference. Swapping in a known good ECU next and reprogramming it to my car next.

 

... REQUEST original ECU to keep as your own spare unit.

Hope the fresh ECU delivers a change...
🤞
Do you trust poor-GND were really worked on before lucky ECU swap??

 

The symptoms of a SAM (fusebox) sorta look like this but it takes out multiple modules at once.

ECU going out can literally do anything but usually i give up on the car as a shop before I diag it as an ECU

 

Yeah current shop is very trustworthy. Very knowledgeable and reasonable. But yes I remain hopeful but I also remain expecting to need to move on to the next possibility. Which in this case would be engine wiring harness.

Thankfully the shop will not charge me for the ECU if it does not make a difference.

 

Any way to rule out the SAM without swapping it entirely?

 

that's what's strikes me here... parts are replaced helplessly by professionals without failing any test.

Straight wet finger parts-canon - This is *** backwards!

Parts are good until proven bad!

 

Well not quite. All the parts replaced by the shops (aside from my preventative maintenance items, tackling the common failure points on the M156), were done because they showed signs of issues.

- Spark plugs, coil packs, fuel injectors - all cylinders - done by me, maintenance items
- All 4 O2 sensors (Bank 2 upstream replaced twice) - possible bad voltage readings, replaced by shop
- Head bolts (updated revision) - preventative maintenance
- Camshaft adjusters rebuilt (63 Motorsports) - preventative maintenance
- Camshaft lifters/tappets - preventative maintenance
- Valve cover gaskets - preventative maintenance
- Crankcase vent valve - preventative maintenance
- Intake manifold resealed - preventative maintenance / ruling out as possible issue, there was a fair amount of build-up
- Throttle bodies cleaned - preventative maintenance / ruling out as possible issue, there was a fair amount of build-up
- MAF sensors cleaned - done by me, easy, ruled out as possible issue
- Camshaft position sensor Bank 2 - seeping oil into harness / was getting bad cam position angle
- Camshaft solenoid Bank 2 - replaced due to bad cam position angle, ruled out as possible issue
- Engine and trans mounts replaced (Creative Steel) - maintenance, these were collapsed
- All bank 2 fuel injector, coil pack, and camshaft solenoid electrical connectors cleaned with electrical cleaner - preventative maintenance / ruling out as possible issu

#### Other:
- Both batteries replaced - replaced before hesitation troubleshooting, these were due
- Full transmission service with TCU reset - due from mileage and prior to misfire discovery when I was thinking it was trans related
- Throttle pedal - replaced from previously unrelated failure of throttle pedal assembly
- Rear driveshaft flex joint - cracked, maintenance
- Alternator (NEW - just installed) - failed completely, replaced
- Radiator (NEW - blown during alternator failure) - failed completely, replaced

So in summary, none of the parts have really been a waste aside from maybe the bank 2 Camshaft solenoid but we were still seeing the odd camshaft position angle. The current shop says the current readings are normal compared to other cars with the M156 he has in service currently including his personal C63.

All the extra costs have come from diagnostic time chasing data to back up replacing parts. I wanted to get data to back up replacing the ECU or wiring harness and we have some data to lead to this now. Voltages going to the coil pack for cylinder 7 are definitely contributing to the misfires. Current shop doesn't have a suitable oscilloscope to test this while driving but it was tested at idle. And apparently testing to rule out a faulty ECU that isn't throwing codes in Xentry is hard to come by.

ECU isn't expensive to swap, relatively speaking... So next logical step will be the wiring harness considering we know we have electrical issues. The ECU is commanding odd voltage from the alternator. Current shop disconnected the LIN wire and the alternator started providing solid voltage between 13.8-14.4V.

 

I get it... these shops use their own logic I am not sure I follow. I can see swapping hot ECU, why not. Sometimes it's best to make progress...

So you know: the engine harness job is also called the "$10k job"... not a quick deal.
A scope cost way less than $500, if they know believe an ECU signal is poor it's easy to look at it compare it for frequency and voltage/shape: 10mn done, no parts!

Here is scope

 

Oh yeah I’d definitely get some data to back up needing a new harness before going that route… which we already have somewhat knowing the voltages going to the cylinder 7 coil pack are not correct / out of spec.

 

I got you a bypass shortcut:
If your coil-7 signal is still bad after ECU swap
then save your harness by routing a new line from coil-7 to nearby ECU.
Call that 30mn labor, not $10k.

++++ Bad signal, really?
Without daring to question coil-7 diagnosis.


++++ "$10k-Oil-in-harness":
PM for a cheap workaround (free!).

 

That honestly does not sound like 30 minutes of labor to me lol. And wouldn’t explain the other minor misfires on the bank.

I think I’m also too far into this car to have a ad-hoc wire ran for a coil pack of all things. I’d want to do things the right way. Which might be splicing the wiring harness instead (short of a whole new harness).

Regardless, we’re not to that point yet. I’ll cross that bridge when I get there!

Also I wonder why it’s $10k? The current shop has mentioned it wouldn’t be engine out. Used wiring harnesses are sub $1k. I don’t have a quote but I’m feeling like it wouldn’t be $10k anyways at the current shop.

 

Go for it!

 

yes indeed, splicing is exactly what the shortcut is about to bypass "bad line(s) to coil-7"...

It starts with a rough wiring strap that quickly proves or disproves the whole procedure will be effective.

The preliminary answer is available is less than 15mn before going through all the pain of a clean bypass installation.

So the initial step is A STOP OR GO TEST using quick strap(s).
Besides scoping can help clearly qualify the "bad signal" before any harness work.


I don't exactly know why dealer charge $10,000 for a harness - Engine out may help save technician time.

You want result without big-tag... now you can save serious time.

+++ $10k harness job
is a repair for "oil in harness" not "questionable harness"...
Harness better be "known bad" first.... yes?

 

because this is a what we read routinely with wire harness replacement, definitely inflated dealer prices but it is what is reported, glad you have a tech that can do it for $1k

https://mbworld.org/forums/w212-amg/...ml#post8569327

https://mbworld.org/forums/w212-amg/...sors-leak.html