W639 - alternator issue & EGR/MAF odd readings

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New Member
Aug 11, 2021
Vito W639
Hi there,

Just signed up, been a long time reader of the forum, always very useful so thank you

I have an '04 W639 Vito 111 Dualiner so it is showing its age by now (only done 160k miles however) with plenty of rust to sort out :-(

It has recently developed an issue with the alternator I think, at the start of a long drive recently the battery warning light kicked in and the revs at idle kept jumping a little. I could carry on driving and got home OK but there were a few times when the dash computer restarted (showing an error code -183) whilst driving which wasn't a pleasant experience. At home I got a voltmeter on the battery when engine running and the voltage would jump to ~13.5V to indicate charging briefly but then settle to around 12.3V for a longer period, this cycle would then repeat. So I'm suspecting my alternator to have a problem but it's strange that it is trying to charge but only does so for a short time

I also have had a longer term issue of the dreaded EGR/MAF problem - warning codes have come up for the EGR in past but some mechanics have cleaned the valve and said it looks fine but this hasn't cleared the engine error light.

I have suspected the MAF sensor needing a clean or being faulty and I have recently bought an ODB reader to check the live data:

At idle MAF reads 0.0g/s and even when revving this value doesn't change

The EGR values are as follows:
EGR_PTC(%): 4.7
EGR_ERR(%): -100.0

Do these values look suspicious? I'm guessing the MAF should be reading something even at idle?

I'm using a FOXWELL NT301 ODB reader but it couldn't detect any error codes, maybe I cleared them by mistake. I will try again to see what it can download

Thanks for any tips/help!
Cheers, Alex
how did you sorted out ?

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