P0102 VCDS - MAF need replacing?

[Rog_B]

Hi all, my good friend Alex that I met on here very kindly scanned my 2.0TDI 140 and this code came up. The car runs great, though. When I did my service and filter change, I cleaned out the EGR too, and the MAF very carefully in a bath of isopropanol without touching anything delicate.
Any ideas from the clever folks? All the wiring seems sound and I can't detect any air leaks.
Thanks
Rog
(PS mine is on the Audi/VW "naughty" list, might not bother getting it "reset" unless they decide to hand over bags of dosh to compensate lol!)

000258 - Mass Air Flow Sensor (G70)
P0102 - 000 - Signal too Low - Intermittent
Freeze Frame:
Fault Status: 00100000
Fault Priority: 2
Fault Frequency: 1
Reset counter: 255
Mileage: 105819 km
Time Indication: 0


Freeze Frame:
RPM: 0 /min
Speed: 0.0 km/h
Voltage: 12.08 V
Load: 100.0 %
Load: 100.0 %
Mass Air / Rev.: 765.0 mg/str
Mass Air / Rev.: 0.0 mg/str

 

[fouryoghurts]

"Signal too low" is the result of the actual airflow, as sensed by your air mass meter, being less than the predicted amount when compare to the map.
A primary function of the air mass meter is to monitor the operation of the EGR valve, essentially providing closedloop feedback. So for instance, if the air mass meter detects a value less than expected the EGR valve and may be stuck open despite the ECM telling it to close. You are correct to mention that an air leak can also cause a similar problem.
The ideal initial test to check correct operation is to monitor live data for both EGR position, pulsed control (from ECM) and air mass. If this looks okay the next step would be to check peak voltage under load (during road test) on the air mass meter - your air mass meter may be undervaluing air flow. A final test to confirm that your mass meter is operating within specification would be to carry out a "still air" test. This involves removing the air mass meter from the intake tract, capping both ends and, using an oscilloscope, monitoring the output signal voltage... Which is then compared to the manufacturer's specification.

 

[Rog_B]

Wow thanks 4Yogs, that is a stellar reply for sure! So..... might be an idea to change the MAF then?
I have got a scope that runs from my laptop, but I'm not sure about doing all the other stuff, as I have to get my buddy to fire up the VCDS again, he's done so much for me as it is.

 

[fouryoghurts]

The above assumes it's a hard fault...although, it's always nice to know your air mass' peak voltage
If your VCDS guy can clear the fault, see how you get on before cracking out the scope.

 

[Rog_B]

Just to update, I replaced the MAF with a lovely new one from Super Mike mjr901 and the engine is running great. I haven't rechecked with VCDS but all seems to be running well. Idling is rock steady too.