Help with Maf Sensor

[hadley8899]

 

Hi Ive recently purchased a fairly high mileage MK5 GTI 2005 plate.

Ive done the following fixes so far
- Changed the cam follower (Was very bad)
- Changed the diverter valve (Was split)
- Changed the thermostat (Temp was down at about 60 at all times)

Ive now got an issue with the eml light. Its the code for the P0100, Its the Mass airflow sensor, So ive orded a new one and its arrived today, Plugged it in and I seem to have no reading from it.

It seems to read 655 at all times (Which probaly means its not detecting anything from it).

Any advice on what I can do now?, Wiring and connection looks ok. I havent looked any further than just the wires you can see without pulling apart the loom

Cheers
Ryan

[Clarkj93]

Where did you get the MAF from? Genuine/after market? New/second hand?

[hadley8899]

Went for a good old AutoDoc Special

https://www.autodoc.co.uk/autlog/14502499

[pudding]

Hmmmmm 

What scan tool?  655 doesn't mean anything.  It should show a reading in grams/sec, which should be around 2.5g/s at hot idle.
 

[hadley8899]

Yeah its 655g/s. Its the max possible reading the sensor can give from what I can gather, I assume its what the ECU defaults to if it cannot get a reading from it.

I suspect a broken wire or worse a f**ked ECU, I take it the MAF sensor goes directly to the ECU? Which isnt really to far away from where the sensor is sat

Not really sure what else it could be?

[Clarkj93]

Yeah its 655g/s. Its the max possible reading the sensor can give from what I can gather, I assume its what the ECU defaults to if it cannot get a reading from it.

I suspect a broken wire or worse a f**ked ECU, I take it the MAF sensor goes directly to the ECU? Which isnt really to far away from where the sensor is sat

Not really sure what else it could be?

My uneducated guess would be a wire but I have no faith in stuff AutoDoc sells to be honest. Does the old Maf give any reading at all or same result?

[pudding]

Hmmmm, I'm not sure GTI MAFs can read as high as 655g/s.  That's enough for over 800hp 

It won't be the ECU.  More likely the sensor or a wiring problem.  If the engine has an aftermarket intake kit on it, the latter is a possibility.  The ECU does normally flag any wiring issues, such as "Short to B+", "Short to Ground", "Implausible signal", "Open or no signal" etc etc.

[hadley8899]

Maybe my diagnostics is just crap... Its the TOPDON ArtiDiag500. Its either I dont know how to use it very well or it just doesnt give this kind of info.

Ive asked a local mechanic to come and have a look, He said hes dealt with this issue before and everytime hes done it its been a broken wire so ill see what he says.

Ill post what happens when I find out.

Cheers

[hadley8899]

This is the data from a drive out I did while recording yesterday. Its just a constant 655 which would indicate its just doing nothing at all




Cheers
Ryan

[pudding]

Yeah if the number doesn't move at all, definitely fooked.

I think there's only 3 wires on the MAF.  You could do a continuity check back to the ECU pins if you're bored?

[hadley8899]

Just as a follow up to this, The job went a bit sideways

So after checking the pins to the MAF using the following guide

https://workshop-manuals.com/volkswagen/gti/l4-2.0l_turbo_(bpy)/powertrain_management/computers_and_control_systems/air_flow_meter/sensor/component_information/technical_service_bulletins/page_5084/

I got 5v ish on the yellow wire, Perfect ground on the brown wire but no battery voltage on the black wire

Note I neglected to mention that I also had the following codes

01314
p0100
p2188

I didnt think they were important at the time, Turns out they were a big hint. I tested the black wire on the MAF to fuse 29 (I think) in the interior fusebox and got no connection. Turns out I had a broken wire right down in the harness below the battery which ended up being really hard to find.
Fixed this wire all all is right in the world.

Apart from the fact I found the previous owner had shoved a bolt in the pipe from the PCV to the inlet, So I take it he knew the PCV was bad and did this bodge but thats a topic for another day

Cheers all for the help, Really appreciated

[RBS]

Maybe a long shot but have you deleted the fault code in VCDS after installing the new MAF sensor?

[hadley8899]

Yeah cleared all the fault codes, Can see a good reading for the maf now about 2 ish g/s at idle and goes up and down with revs.

Looks like the issue is all fixed, Atleast for now. Ive got a hunting idle so ive ordered a new PCV and pipe which is coming today that will sort that issue (I hope)

[Greek_GolfV]

The does have stock ecu? Or custom map?