2004 W211 E320 CDI - turbo trouble

[AlexM]

Hi All,

My 2004 E320 CDI estate started displaying a check engine light and going into limp-home mode, so off it went to M-B Epsom for diagnosis.

It turns out that the VNT vanes on the turbo were stuck, and after this had been freed up mecanically, the actuator was bot working. The consequence was that the Turbo needs replacing with a reconditioned or new unit.

As my dealer wanted £1200 for the job and I can source a new Garrett VT23 for £450, I am considering having a local garage do the spanner work.

My question is:

a) are there any specific procedures required to calibrate the turbo via the ECU?
b) Will check engine light go away once the turbo is replaced, or is a reset required?
c) Any other work likely to be required?.

Very disappointed that the Turbo has sufferred a failure after only 43k, but this seems to be a common issue.

Thanks in advance for any tips or info.

Regards,
Alex

 

[Alex Crow]

it is pretty much just a matter of fitting the turbo and erasing the codes.

watch the bolts to the manifolds, they can be super tight and shear off.

also note that the exhaust manifolds on some of these 642 engines (assuming V6 here, they love new turbos and inlet port shutoff motors...) have an issue with delaminating plating on the inside that can in turn jam the vanes - according to MB at least.

 

[AlexM]

Hi All,

OK, this is going from bad to worse!. I managed to source a new turbo, which has been fitted to the car by my local independent.

Initially on their test drive, the car seemed to be boosting correctly, but after a couple of miles it went into 'limp home' mode (no boost/kick-down), and was showing a check engine light.

Scanning the codes shows the same fault as before the turbo swap (2510001 - charge pressure positioner signals fault).

The garage is checking for continuity/shorts in the wiring, but are saying that it could be an ECU fault. They seem to be struggling to locate the problem.

They say that the EGR valve cycles normally on command, and that the MAF seems to be ok.

Any suggestions? All further part swaps from here are likely to be very expensive - I may have already replaced a turbo that was fine!.

Thanks in advance for your help.

Regards,
Alex

 

[davidjpowell]

Did anyone check the Port inlet motor for oil contamination? I'm not sure what error codes it kicks off, but it's a classic symptom and fault on the V6.

Others will definitely know more than me!

 

[jaymanek]

Im assuming you changed the positioner as well as the turbo?

 

[AlexM]

Sorry, should have clarified, but my car has the in-line 6 cylinder engine rather than the V6.

I assume that the VNT actuator is providing position feedback, i.e. position x commanded, position y achieved, and that any mismatch is causing the error to be logged. Are there any other candidates that might cause this error code? Manifold pressure sensors, MAF underreading, vacuum lines or sensors?.

As you can tell I don't know much about how this car works - have owned several petrol turbocharged cars before, but no experience of cars without a waste gate, so I have no idea how boost control works on a VNT diesel.

Thanks,
Alex

 

[Druk]

2004 will be straight six engine. There's a boost pressure sensor on the inlet manifold N/S can go wonky and car goes into limp home. Fixed it for me.

 

[AlexM]

Jaymanek,

The turbo was supplied as a complete assembly including actuator and control unit - presume this is what you were asking.

Regards,
Alex

 

[jaymanek]

They need to check if the actuator works... i.e. it needs to be actuated with a star machine.

 

[AlexM]

Believe they have done so... I was told that they can see the actuator moving, but not totally sure whether they used star to cycle it. Not beyond the bounds of possibility that the new turbo is defective, but seems to much too much of a coincidence that it has the same problem as the old one. I am speculating that possibly both turbos were fine and the fault lies elsewhere.

I was also told that they could open and close the EGR on command, so presume that they are using star.

Regards,
Alex

 

[jaymanek]

Could be,.. we have seen bad ECU's, bent pins on ECU's.. wiring shorting out...

 

[AlexM]

If ECU were faulty, does anyone repair them? Assume that a new replacement wuld be pricey..

 

[jaymanek]

Yes just google it there are loads and loads of places!

 

[AlexM]

Thanks - was told I was looking at £500 minimum if ECU is faulty. I hope correcting this problem isn't going to turn into a random parts swapping exercise, and also that it might turn out to be a small problem such as wiring or a duff map sensor!.

I'll know more tomorrow...

 

[AlexM]

Hi All,

soo... it turned out to be a wiring problem somewhere in the loom between ECU and VNT controller module on the turbo. Quite suprised to find a loom problem on a relatively new, low mileage car, especially a Mercedes (then again....).

Good news is that it is fixed.. bad news is that the turbo was replaced first!.

Anyone need a lightly used turbo for a W211 E320 CDI? It is probably fine

Regards,
Alex

 

[evdok]

Sell it to the idiots who diagnosed the turbo!

 

[Peter DLM]

Are there any more details on exactly what the loom problem was and what caused it, and the fix?

 

[mobeyone]

Same here, if you could add a quick summary of parts and costs it would be appreciated.

 

[Peter DLM]

 

[AlexM]

The garage told me that there are six wires in the loom between ECU and Turbo. The problem was an intermittent loss of continuity on one of theose, but didn't specify which.

Given that they could move the VNT controller using Star, I am assuming that whichever wires send the position command to the VNT controller on the turbo were in tact. I would imagine that the VNT controller provides postion feedback to the ECU that it has 'achieved' the commanded position, and I think this is was not working, leading to the check engine light illuminating.

I'm afraid that I don't know anything about the pin-out of the connectors on the Turbo, or the command protocol between ECU and Turbo, so I can't be specific.

If anyone has access to a wiring diagram, it might help identify which conductor was having problems, assuming that my hypothesis is correct.

Regards,
Alex