No power issue with new MAF, fault codes on VCDS 2L Bkd

[tdiblacky]

My 2.0L BKD had no power going to work yesterday morning, can get to 80mph but takes ages to get there. Engine management light wasn't on but came on after I drove home from work yesterday evening.

I suspected a turbo hose as had heard one leaking recently, however all the hoses seemed ok, I removed, cleaned and refitted them.
I scanned the car then with VCDS and got 3 fault codes, Mass air flow sensor, Intake air temp sensor + Manifold pressure / Boost sensor.
So, I disconnected the MAF sensor and went for spin, car was no different, so I assumed it was probably a faulty MAF sensor.

Wanted to buy a genuine Bosch replacement as had read of issues with aftermarket. VW wanted €365+ vat, a Febi was €224+vat and a NTK €67+vat. So I said I'd chance the NTK, cleared the codes before starting, fitted it tonight and the car has the same problem.
Engine management light wasn't on, but I scanned it again and have same 3 faults.

Am I correct in believing the Mass air flow and the intake air temp are a combined sensor in the MAF which is the first two fault codes and the Manifold / Boost sensor is a separate sensor?
Is the Boost sensor the one on the lower Intercooler hose where hose enters the intercooler itself?

Is there anything I can check in VCDS (values) that will show me the MAF is working ok or not? ie: what values should I see when idling / driving etc..
And likewise with the Boost sensor, what values should I expect to see when ideling, etc..

Will unplugging the Boost sensor and driving it help me diagnose the issue like what I tried with unplugging the Maf?
Or what's my next step/s do ye folk suggest?

Here are the 3 fault codes:
1 - Mass air flow sensor G70 - P001 Implausible signal
2 - Intake air temp sensor G42 - P0113 - Signal too high - intermittent
3 - Manifold pressure / boost sensor G31 - P0238 - signal too high

[tdiblacky]

I warmed the engine up now, still no power and no EML on whilst driving. I then left it ideling and revved it up to see if it would reach 5000rpm and it could, i only revved it up to 4500 but it was going higher I just didn't want to push it needlessly.
I then turned it off and turned it back on again and the EML is now lit. Does the fact the Eml comes on after turning off the engine and restarting indicate an electrical issue, why doesn't the EML come on during a drive? The EML will still be on the next time I drive it, but when cleared it doesn't come back on during the first drive after clearing, it will only reappear after I switch the engine off and restart and then stays on until I clear it again obviously.

I'm thinking this might be electrical issue, I'd appreciate some members opinions on this. I think I'll check the earths under the airbox and then try probe some of the wires at the Maf for basics like 12v, 5v, etc...
Could a faulty Boost sensor cause all 3 of these fault codes either?

The car isn't smokey and is ideling normally, so I think the Maf is ok. The power loss also happened out of the blue, it wasn't a gradual loss over a period of time like a gradually failing Maf, so I think the Maf sensor itself is ok.
Any ideas?

[tdiblacky]

Done little bit of testing with my multimeter now with ignition on. The MAF has 4 wires and the connector is the 5pin type with only 4 used.
Numbers on the plug:
1 = not used.
2 = Blue / Black has 12v
3 = Green has 0.76ohms (What should this wire have v or ohms?)
4 = Purple / Black has 5v
5 = Black has 11.5ohms (What should this wire have v or ohms?)

Can anyone tell me what wires 3 + 5 do and what values they should have, please? I have updated this post to state the ohms I measured at wires 3 and 5.
No replies, but I'll keep adding to the thread as it might help someone else in the future if I solve the issue.

[tdiblacky]

I cleared the faults again and checked some measuring blocks in VCDS with car running.

This time only 1 fault code returned which is for the boost sensor, so I'm half guessing / hoping this sensor is the problem now. Is this likely seen as it was the only fault code showing?

So I'm going to measure it's 4 wires and inspect them now.

Code was:
005522 - Altitude / Boost pressure sensor - P1592 -000 - Implausible Correlation

[tdiblacky]

Issue fixed, broken brown wire at the Boost sensor. All fine again, hopefully this thread might help someone in future.

It's amazing why the fault codes can't help to pin-point an electrical issue such as a single broken wire, I believe this brown wire is a earth, in fairness I suppose the last fault code that only occured once did suggest bad earhts at the boost sensor but why didn't that fault code come up originally and why did the other Maf codes come up instead.

[mickeybo]

The terminal 2 is correct at 12vs terminal 4 is correct at 5vs terminal 3 is the earth terminal and has to be checked from terminal 3 to battery neg the ohms reading should approx 1ohms im positive you have a wiring problem

[Crasher]

I was going to say this is usually the MAP/IAT sensor wiring, I blame my COVID jab yesterday… feel ****!

[tdiblacky]

The terminal 2 is correct at 12vs terminal 4 is correct at 5vs terminal 3 is the earth terminal and has to be checked from terminal 3 to battery neg the ohms reading should approx 1ohms im positive you have a wiring problem

Cheers, I'm having same / similar issues now few months later.
Is terminal 5 an earth too, yeah?
So there's 2 earths, a 12v and a 5v wire. Is one earth for the 5v signal wire and the other earth for the 12v? Or is terminal 5 something else altogether?