Engine light. MAF Or something else

Hello 2003 tdi wagon with 334,000. I bought this new and put the miles on myself.

Through this forum I met a great person/ mechanic who has helped me through many big repairs but this even he is stumbled with my problem. So the engine light went on. The code said egr. He did a vacuum test and it held vacuum. So replaced the MAF. the light was off for a while then came back on. I then replaced all the vacuum hoses. The light came back on. Then I did a egr clean. The light came back on. Does anyone have any suggestions for what my problem can be? The engine is running very good. It's just the engine light is on.

Thank you very much

What's the code? Possible the EGR gave out.
Lots of folks like to remove those, so if you do need a replacement, they're available.

BobnOH said:

What's the code? Possible the EGR gave out.
Lots of folks like to remove those, so if you do need a replacement, they're available.

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It was pr104 EGR. Not sure of the number but it was the EGR. My friend did a vacuum test and the vacuum held. What else can go wrong?

Can't find that code. Reason I ask is codes do not narrow down components, but rather systems. And there are a bunch that call EGR.
We do see an increase in wiring/connect issues as our cars get old.

I get the "EGR insufficient flow" randomly usually during a coast down. A new EGR valve is in order eventually.
But, the OP needs to get the correct specific code to really know what's wrong. The EGR valve can probably still hold vacuum but be seized and unoperational.

jettawreck said:

the OP needs to get the correct specific code to really know what's wrong.

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...and ideally with a VW-specific scanner, which will catch codes generic scanners miss or mis-report.

Just got the code read again. PO401 exhaust gas recirculating flow insufficient.
Got the code read at autozone.
Hope this helps

That code may be correct.
From the Ross Tech wiki.
Notice bad unit is listed last.

mcarlito said:

Just got the code read again. PO401 exhaust gas recirculating flow insufficient.
Got the code read at autozone.
Hope this helps

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P0401. That's the same code I get randomly (at least that's the code on the ScanGauge). Everything else is fine power and boost wise and thus I assume the EGR probably "holds" vacuum and just doesn't always move as requested. I should check it out w/VCDS but haven't had a reason to be concerned with it much. If/when it comes on it's usually after a coast down and reaccelerating up to speed.

BobnOH said:

That code may be correct.
From the Ross Tech wiki.
Notice bad unit is listed last.

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Actually, faulty EGR unit is second and third on the list. Faulty "system" is last on the list.

so why was the MAF replaced? Is it something he just enjoys replacing?

Ol'Rattler said:

so why was the MAF replaced? Is it something he just enjoys replacing?

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^^^^^

stomachbuzz said:

^^^^^

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It was suggested to me to replace the MAF because it was possible it wasn't working properly. MAF doesn't throw a code even when it's bad. And before that I replaced, all the vacuum hoses and did a vacuum test on the EGR which showed it was good.

mcarlito said:

It was suggested to me to replace the MAF because it was possible it wasn't working properly. MAF doesn't throw a code even when it's bad. And before that I replaced, all the vacuum hoses and did a vacuum test on the EGR which showed it was good.

Click to expand...

Most MAF faults will generate some code.

jettawreck said:

Actually, faulty EGR unit is second and third on the list. Faulty "system" is last on the list.

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Yes, I can't count. Point was to rule out the dumb stuff and diagnose system, not just component named.

BobnOH said:

Most MAF faults will generate some code.

Yes, I can't count. Point was to rule out the dumb stuff and diagnose system, not just component named.

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Oddly, I've had at least one MAF failure in each of the three ALH TDIs owned and none ever generated a fault code or CEL/MIL. Each one acted slightly different in fail mode also.

jettawreck said:

Oddly, I've had at least one MAF failure in each of the three ALH TDIs owned and none ever generated a fault code or CEL/MIL. Each one acted slightly different in fail mode also.

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If it has an internal wiring issue or fails outright it can trip an "signal implausible" code... but if it's reporting numbers but lying about the actual values no way for the ECU to know.

Same with the temperature sensor... no way for the ECU to figure out fake news.

jettawreck said:

Oddly, I've had at least one MAF failure in each of the three ALH TDIs owned and none ever generated a fault code or CEL/MIL. Each one acted slightly different in fail mode also.

Click to expand...

Can't argue with real world experience!

Come to remember, mine did that once, years ago I was running the infamous K&N filter.
Guess it doesn't know when the hot film sensor is trashed.