Help with fault codes

Hiya guys just signed up to the forum! Had td all my life bur always had Peugeot's. Anyway I got a mk 5 golf gt tdi 140 remapped to 180ish.

Main problem I have is lump mode at around 60mph. Read the codes and have the following.

P0299 - underboost condition

P0101 - Mass or Volume Air Flow "A" Circuit Range/Performance

P0401 - Exhaust Gas Recirculation "A" Flow Insufficient Detected

The EGR is more than likely because it's been capped off so that's OK for now.

Mass air flow does that mean possibly dirty sensor?

Now the underboost is my main concern as I think this is what trips limp mode. The car apparently had a new turbo last year so hopefully it's not that. Maybe a leak? The tuebo does whistle loud but not sure that's how the car is or maybe because it's been remapped?

Is there any live diagnostics I can do to help figure this out? Any help would be very much appreciated.

Thanks in advance



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if you hear a whistle while normal driving you probably have a leak somewhere. I would check all your boost hoses.

Also since your under boosting and you have a mass air flow code I would think your not getting the amount of air that you should get thats you should see.
Basic thing to check is the Air filter see if its clogged then check for boost leaks.

One relatively easy thing to do is to check the vacuum system pump, hoses and the vacuum reservoir for leaks. The turbo boost function is vacuum operated and will not work without enough vacuum. Measuring the actual vacuum seems to be one thing VW seems to have left off the list of things for the ECU to do.

Thanks for the replys. I will check for leaks today . One thing I did do was clear all the codes and take the car for a drive. Got to 60 and limp mode again except no eml light on? I would of thought it would of come back on?

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it takes 2 trips for the mil light to come on unless its a major issue which will turn it on right away like a dead misfire.

O right. Thanks chaos!

chaos2984 said:

it takes 2 trips for the mil light to come on unless its a major issue which will turn it on right away like a dead misfire.

Click to expand...

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Yes check leak in vacuum lines and Zip tie mod.

Checked all the Vacuum lines and can't find any leaks. Surprised that they wasn't even cracked at all. They may of been changed in the past. I need to get a closer look around the turbo but there may be a leak down the back on the left as a black pipe looks cracked. I'm pretty certain it is a boost pipe as it's a large pipe.

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Can anyone understand this scatter chart?

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