They Said it Can't be Fixed - A Journey to the Inside of a Mercedes Bluetec

Well, that didn't take long.  Back in limp mode and now it's throwing codes that seem to indicate that the DPF pressure sensor isn't right.  That's a short to ground on the swirl motor, an electrical fault or open circuit on the O2 heater circuit, and now dpf signal voltage too low.  I am fairly certain that the computer was replaced as part of the AEM, so I can probably rule that out.  I think I'm going to need to get up close and personal with the wiring harness.  Naturally, it does this while I need to get the clutch done on the Mazda 5, so it's just going to have to be driven around like this until I can get that done.

In reply to Pete. (l33t FS) :

Got a bottle on the way!

wae said:

Well, that didn't take long.  Back in limp mode and now it's throwing codes that seem to indicate that the DPF pressure sensor isn't right.  That's a short to ground on the swirl motor, an electrical fault or open circuit on the O2 heater circuit, and now dpf signal voltage too low.  I am fairly certain that the computer was replaced as part of the AEM, so I can probably rule that out.  I think I'm going to need to get up close and personal with the wiring harness.  Naturally, it does this while I need to get the clutch done on the Mazda 5, so it's just going to have to be driven around like this until I can get that done.

Two good-running Mercedes in the same place must have ruptured something in the space-time continuum.  We'll need to keep them separate in the future.

Here's my update from Bluetec hell, specifically since the emission recall work:

Noticed a hot diesel fuel smell while walking around the front of the truck. Opened hood, definitely could smell diesel coooking off underhood. Pulled aircleaners & batwing & sound deadener foam. Found fuel on RH valve cover, apeared to be emanating from middle cylinder injector fitting. Fiddled around, managed to get a 17mm line wrench on the line nut and put 1/6th of a turn on it. Need to test drive to verify, but confidence is high that seals it up.

The dealer tech discarded my high tech fabricated M55 motor protector and left out a couple of firewall heatshield bolts. I replaced bolts, but didn't re-fab oil protector since the new batwing is sealing well, not dripping oil on M55.

Also noticed a lot of oil in PCV hose, batwing and turbo inlet. Oil level is down about half a liter on the dipstick, since the rebuild was completed back in May, about 1500mi ago. There is a Mann ProVent waiting to be installed in the breather line, this is indicating it needs installed sooner rather than later. The oil mist getting pulled into turbo ends up sludging the intake valves, ports, manifolds and also puddling in the low points of the intercooler.

Installed 4 new Pirelli Scorpion A/S tires, in place of the worn out RFT tires. A great improvement in ride quality, but slightly squirmy handling on green tires, compared to 'shaved to race depth' tires that came off. Hoping there will be a MPG bump with conventional LRR radials, vs heavy RFTs.

On the self-inflicted weinerschteppin aspect of this project. Tried connecting trailer brake signal wire from rear SAM to the CHMSL output at SAM. Unfortunately it didn't work at all, plus it appears to have blown up the SAM. The dash is indicating "bad 3rd brake lamp" and "bad license lamps". The electric hatch release (the only hatch release) is also inop. Basically, everything in tailgate is inop. The SAM was full of codes for CHMSL short to power, short to ground.... Tried clearing codes and resetting all modules, no joy. Need to flatten seats and climb back there to rear fusebox and check for blown fuses, maybe I'll get lucky...

In reply to FJ40Jim :

That reminds me that I need to check the oil level in mine when I have a second.  It was holding steady for the first thousand, but I definitely have a little bit of a drip somewhere.

I have it on good authority, though, that the technicians at the Mercedes dealerships are the only qualified technicians or mechanics in the world.  So clearly you must be mistaken about them not tighening up the fuel pipes all the way.

I read these threads to remind me never to stray away from Japanese cars unless I can afford someone else to fix it out of warranty. YIKES

fidelity101 said:

I read these threads to remind me never to stray away from Japanese cars unless I can afford someone else to fix it out of warranty. YIKES

I got sucked in despite these threads, and knowing wae personally.  At least I did not get a diesel.  It's a weird bit of cognitive dissonance, knowing my E-class feels a lot more solid than my Lexus GS did, but knowing in reality, it is far more delicate.

fidelity101 said:

I read these threads to remind me never to stray away from Japanese cars unless I can afford someone else to fix it out of warranty. YIKES

But when they're running right, they drive like nothing else....  And, really, the diesels - specifically the BlueTECs - are a whole different can of reliability worms.

I know, it's all just excuses, excuses.....  I dated a girl like this once and while I definitely dodged a bullet on that one, I feel like maybe I didn't really learn my lesson.

I am putting a VQ40 in a late model Nissan truck because the block corroded away from the main oil passage...

While still waiting to install the rebuilt om642 in the sprinter I got sidetracked with 716.638 6 speed manual transmission from a m272 powered C class. The plan is to install it in my w211 wagon. But while I had the transmission side by side with the om642 I couldn't help notice that it shares the same bell housing bolt pattern as the om642. So if you ever run out of problem to fix on the 642, you could always take on a manual swap. 

Also added an oil pressure sensor to the om642 using an m18-1.5 to 1/8 NPT adapter. You would think a heavy duty or commercial vehicle like the sprinter would have an oil pressure gauge or at least an oil pressure idiot light from the factory.

NOPE

Hopefully start the engine swap into the sprinter this weekend. 

EDIT: for anyone reading this in the future, the connecting rod bolts are stretch bolts. New length spec 47mm, max reuse length 48mm. 4 of 12 we're beyond 48mm. New bolts measured 46.7mm. Just replace the damn things. 

This is a lot of paperwork work a 15ml bottle.....

Oh good, you got the little brushes too.  Those help economize since you can put a drop on the brush upnat eye level instead of squirting half the bottle at a connector.

I finally have a couple minutes to try to troubleshoot.  I read that someone else from the mbworld forum had the exact DPF and DPF sensor codes that are putting me in limp mode.  It was post-AEM and they said the warranty covered it.  So I'll check the wires and if they test good, I may just send it back to them.  First, though, I want to check out the O2 heater wire that connects back to the CDI Control Unit.  I also want to check the wiring for the M55 motor.  What I am trying to avoid is having these fools spend fifteen hours of $180/hr labor to come back and say "oh, your wiring harness is bad and none of that was covered by the extended warranty".

For those of you playing the home game, the CDI control unit is a little hard to find, if you follow WIS.  They said that it's on the right side of the engine bay under the windshield.  What they meant to say is that you have to pull the front right wheel off, take out the back half of the fender liner, and then you'll find the CDI control unit jammed between the monocoque and the fender up and behind the right front tire.

Before I can go any further, though, it's arts-and-crafts time:

fidelity101 said:

I read these threads to remind me never to stray away from Japanese cars unless I can afford someone else to fix it out of warranty. YIKES

Just the Mercedes bluetecs to be avoided lol.

However, Jaguars...

In reply to Glutton4pain :

Yep all Mercedes V engines of that era share the same pattern. 

Well, interesting.  I checked resistance from the pin on the CDI connector to the pin on the O2 sensor connector.  Something like .3 Ohms.  Same between the +12v side of the circuit to the fuse.  So why am I only getting 8.some volts?  I'll use the Stabilant before I hook it up, but I'm a bit perplexed.  I thought that I tested the circuit without the O2 plugged in and got the same voltage readings.  And I know that I got 12V when I used a body ground instead of the pin on the connector.

Also, since it was only $26, I ordered a new DPF sensor from FCPEuro.  If that fixes it, I may put the old one back on and make the dealer spend time with it.

Where are you measuring 8v, and is that with the sensor plugged in?

In reply to Pete. (l33t FS) :

I'm checking across the two terminals that say they're for the O2 heater circuit at the connector from the engine harness to the sensor.  It's been a minute but I'm fairly certain that I tried with the the sensor connected as well as disconnected.  Checking across the terminals gives me 8v, checking from known solid +12v source to the ground-from-ECU gives me 8v, and checking from the +12v terminal to body ground gives me 12v.  I'm 99% sure that they replaced the ECU as part of the AEM so that should mostly rule that out.  I would think a bad ground to the ECU itself would manifest in a dozen and a half other ways, but perhaps I should backtrack that a bit and see.  A distinct possibility could be that the pin in the connector to the ECU just isn't making good contact.  Although, I would think that if that were the case there should have been a good chance of that being fixed when they replaced the ECU and seated the connector.

Ah, okay.  The computer is not pulling it all the way to ground.  A lot of computers run PWM to the heater circuit, and they all monitor current through the heater to determine if it is warmed up and for error detection, so this may be normal.

The Nissan NV1500 that I am putting an engine in tomorrow had a 3v drop through the computer.  Replacing the sensor made the computer happy, so I assume that is normal in that situation.

In reply to Pete. (l33t FS) :

Well, good thing I've got a new Bosch sensor sitting on my workbench!  I'll pop that in along with the DPF sensor and that should get me 66% of the way to turning off the CEL.

wae said: that should get me 66% of the way to turning off the CEL.

You poor deluded man.  Have you learned nothing about German car electronics?

I didn't have time to swap out the O2 yet, but I did put the new DPF sensor in.  No more limping!  Getting to the O2 is kind of a PITA.  I'll take another look at the access to it before deciding, but I might wait to put that in until I'm pulling the turbo to put a new cartridge on it.  I know I'll have all sorts of room with the turbo out.

I sent the rear body SAM to an electronics shop that claims to be able to fix them.  They 'fixed' it in a day, got it back today. Installed SAM, connected battery, reinitialized all windows, steering, etc....

And the SAM still won't energize the CHMSL, license lights or power hatch release. So tomorrow will be spent pin testing connectors at SAM to verify continuity to everything in the rear hatch. If all checks good (and it should), then it's gonna hafta go to the local MB specialist that has the old dealer scan tool for this car, so they can install a new SAM and SCN code it to the vehicle. $400 in parts and prolly about the same in labor, sigh.

On the plus side, a check arrived in the mail today for $2764.xx from Bluetec settlement fund!

Woohoo!  I'm hoping my check shows up soon.  Mainly so I can finally answer my Dad.  At least two times a week - often more! - he asks me if I've heard anything yet.

I decided to be brave today.  I needed to run to Frankfort to get a copy of my daughter's birth certificate so I took der Scheißwagen.  I forgot how nice it was to drive on the open road!  Hopefully my luck holds out and today is a Blanton's day here at the Buffalo Trace distillery.  And that I'm not too far back in line to get a bottle!