MAF wiring diagram/help

[Guest]

Further to my post on turbo overboost problems causing limp mode and EML.

 

Diagnostics show a value of zero for MAF airflow which doesn't change with engine rpm.  When I unplug the MAF sensor I see a value of 550 at idle.

 

I'm looking to check the wiring and could use some pointers from some of you sparkie types, I recall a post somewhere about a failed solder joint at/in the ECU.

 

2006 1.9 BKC

[Vrsburnzy]

Sorry I’m unsure if I’ve missed your other thread but I’m guessing you’ve replaced your MAF sensor?

 

i do have elsawin I can have a look later 👍

[Guest]

@Vrsburnzy

 

Thanks, any help is appreciated before I start reducing things under the bonnet to component parts!

 

Here's the background story:

 

 

[Vrsburnzy]

It looks like I’ve already replied on your original thread 🤣 have you driven it with the maf unplugged? Does it still enter limp mode?
 

I wouldn’t rule out your second maf isn’t duff either, but here is your wiring diagrams.

g70 is maf and j248 is ecu

 

Terminal 5 goes here, the cable with 153 at the end if your not familiar 👍

 

[Guest]

@Vrsburnzy

 

Thanks for the info, unfortunately further work will have to wait for better weather.

 

I have driven with the MAF unplugged and it seems to run smoother but still craps out at 4K rpm or 70mph-give or take.

 

The overboost DTC remains but is accompanied with an additional relating to MAF being unplugged and EML is lit.

[Vrsburnzy]

Iirc it shouldn’t go into limp mode with the maf unplugged, it’ll run a little flat and EML light will come on but not limp.

 

although your maf issue will need resolving.

 

i would say your turbo is looking very likely though, or your n75 but that is the black box thingy on yours isn’t it?

[Guest]

Due to the weather it's been a couple of weeks since I've had a chance to experiment and I'm pretty sure I still got limp mode with the MAF unplugged.

 

Re turbo, I'm confident the rust I found in the solenoid valve block (n75?) originated from the VNT actuator, as it sits upside down water could sit in the depressed centre potentially rusting through.

 

A bit like how the A/C HP sensor failed on mine, bad design, even the fuel filter top catches water run off from a wet bonnet being raised and screenwash refilling splashes.

 

If it's damaged internally you'd think it would trip an underboost DTC, but as it is, it takes and holds vacuum so appears to function normally.

[Vrsburnzy]

Well if you dissect your overboost code, what is happening is the vnt is pulled to its fully open position at idle, as you accelerate the vnt is moved further out closing the vnt making it harder for the turbo to make boost, but yours isn’t, it’s getting stuck somewhere and the turbo is producing too much boost and tripping limp mode.

 

the maf sensor isn’t helping issues but you shouldn’t really be getting limp mode with the MAF unplugged as it reverts back to a failsafe map and your MAP sensor is still controlling boost as it should be.

if the n75 is working correctly then my next step would be to take off and inspect, strip and clean the turbo, the mr muscle trick sometimes just won’t cut it.

 

[Guest]

I have my doubts that the turbo is coked up.

 

The mechanism works freely from stop to stop, the way I drive, with BP Ultimate diesel and the occasional fuel treatment I suspect it's fine.

 

I did see an interesting clip of a VNT being fixed where the control lever had elongated its corresponding notch in the nozzle control ring causing slop in operation.  The ring was welded at the worn spot and reprofiled.

 

In any case I'm in no hurry to take the turbo off, let me deal with the electrics first, which judging from the weather forecasts will be a couple of weeks before I can tackle anything.

[Guest]

I just found out WOW! has wiring/ECU pin-out diagrams so when weather permits I'll check and share my findings...  Y'all have a happy Easter meanwhile!

[Guest]

That's all the sensors checked and everything seems on par.

 

This was an aside to finding out why my car was overboosting (another post).

 

Now hopefully fixed, diagnosed as mechanical after all, a shagged out actuator return spring and adjusted rod to compensate.

 

Thanks for taking time to help Vrsburnzy.

[wexti]

On 27/02/2020 at 11:06, Vrsburnzy said:

Sorry I’m unsure if I’ve missed your other thread but I’m guessing you’ve replaced your MAF sensor?

 

i do have elsawin I can have a look later 👍

Just wondering if you still have access to elsawin? I need the ecu wiring diagram, specifically the pins that go to the turbo actuator. I've a separate topic on this..

 

23 hours ago, b1ackb1rd said:

This takes me back 2 years to the issues I had with my 1.6tdi CAYC. 

 

I've added an additive to every tank since then, injector cleaners, Archoil, the VW additive G001790M3 at least twice, I've used DPF spray cleaners about 4 times through the o2 sensor and manipulated the nozzle so lots went into the turbo, and reverse squirted through the cylinder head towards the EGR valve (dunno if it helped, but when you're cycling the ignition every few hundred yards you get desperate!)

 

Actuator is now free, I don't get limp mode, ever.

 

I have a small pile of MAF, MAP, N75 sensors, oh yea and I also cleaned the ASV of muck.

 

The car now regens well every 300 odd miles, it revs to 4500rpm, and since remapping the EGR valve out it goes really well, with real world economy around 45mpg extra rural on A & B roads.