2015 Audi A4 2.0 tdi limp mode

[gregg]

Hi all, back again after a while. Bought a new car for the wife but having trouble with it. Glow plug light cones on whilst driving and drops into limp mode with no power. Happened when it came and as i was working at the time my bro had plugged into it with vagcom. Showed up egr valve fault and turbo boost pressure not reaching minimum threshold. Replaced egr valve but still the same. I then got a chance to read dtc's myself. Threw up 2x boost pressure codes, 2x maf codes, 1x egr circuit fault and cyl 3 pressure sensor fault. Replaced plug with genuine vag one and code left.

At it again yesterday and today and left now with following codes

P0101 mass air flow sensor - implausible signal

P0401 egr system - insufficient flow

P0299 boost pressure regulation - control range not reached. This code is logged twice.

New egr valve isnt a genuine one but one that we got is supposed to be high quality. Would a genuine one be better?

Tried to attach the pics i took of fault codes but not sure how too.

Tia

[Deleted]

Hi Gregg,

What diagnostic equipment have you access to for investigations?

The parts cannon is a very expensive route and very well might not provide the end result you need! 

[gregg]

Hi guardian

We have vagcom at garage which is what i used for these codes. Also got a loan of a snap on solus which provided the same codes. Forgot.to ad it is the newer cnhc engine with adblue system. Yeah i k iw the parts can get silly. The new egr valve was around £210. Although our local vw dealer supllied the glow plug for £83 all in with our discount. Interestingly enough although they cant supply audi specific parts he can price them. Was surprised to find out that a genuine audi egr valve is around £170+. Would have thought it would be more expensive.

[Deleted]

So the CNHC engine, which car model ar we referring to?




MANUFACTURER
: Audi

ENGINE CODE
: CNHC

MODEL
: Engine Output kW (DIN hp) rpm Tuned for Year


A4 allroad (8KH) (09-16) 2 120(163)4000 2013-2016


A4 (8K2/8K5) (07-15) 2 120(163)4000 2013-2015


A4 quattro (8K2/8K5) (07-15)

[gregg]

Hi guardian

We have vagcom at garage which is what i used for these codes. Also got a loan of a snap on solus which provided the same codes. Forgot.to ad it is the newer cnhc engine with adblue system. Yeah i k iw the parts can get silly. The new egr valve was around £210. Although our local vw dealer supllied the glow plug for £83 all in with our discount. Interestingly enough although they cant supply audi specific parts he can price them. Was surprised to find out that a genuine audi egr valve is around £170+. Would have thought it would be more expensive.

[gregg]

2015 A4 technik se ultra 2.0 tdi 163 bhp

[Deleted]

I've inputted your data into the A/D system and its worse than ever nowadays, fault codes just advise look for a leak and change the part, wiring diagrams don't exist anymore, and checking data is a very long distant memory. Not sure what I am paying them over £100 per month for?

[gregg]

Yeah not a lot to go by then lol. This is my first time seeing this new engine, i'm more used to the previous generation 2.0. After using the dpf cleaner yesterday i got the dpf light illuminated on dash. I took car out and down around 10 miles in 3rd gear at 50mph and light went out after 20 mins driving. It did use some fuel during this so i assume.the dpf done a regen. Aftee coming.back to garage echaust was hot but not scalding. Before thishappened i did notice on previous runs that qhen i stopped driving the dpf was clicking and creaking with a slight blue colour at joint where turbo bolts on. Also was a bit of soot on inner guard beside turbo. Made me.think that dpf was.blocked up and turbo was breathing any way it could.

Now as i say i keep getting the turbo boost below threshold and air mass meter faults. Car seems to have plenty of power before light comes on and drops in power. Cant figure this out. There is a load of sensors between turbo and inlet manifold so not sure where to start or what to look for. Sorry for the vagueness of faults just getting a nuisance now.

[chippie]

How quick does the eml light come on after start up?

I aint no expert, but....
Would have thought looking at live data for dpf would give some indication of blocked dpf - high delta P ?

Turbo boost pressure- how is the boost pressure regulated? Any mechanical mechanism working as it should? I.e not stuck/siezed...

MAF air flow- air filter clean? All ducting leading to throttle body intact? No leaks....?

[gregg]

Hi chippie

Light only comes on after driving 5 mins or so, sometimes comes on driving on sharp other times just steady driving. Air filter clean and all ducting into airbox is clean and clear. Found one sweet wrapper but nothing to cause this. Turbo has vacuum operated wastegate with electronic position sensor. Wastegate is free. I disconnected pipe and i'm able to work it fully by introducing a vacuum into the pipe. Moves freely with no problems. Couldnt find the pressure readings on vagcom but can take a look again to see if i can find it.

[Deleted]

You could try clearing the fault codes and then plug in the scanner and record data while driving car and hopefully the limp mode will happen while driving, and then stop and save data. Play back and do comparisons to see which data stream goes off on a tangent. Power loss while driving I'd probably be looking at things like EGR and any vacuum operated devices like swirl chambers etc if fitted. 

Just a thought if you have a solus and can record data using that, you could upload the results after road test and I could run them in shop stream and have a look for you!

[gregg]

Yeah il give this a try and see if i can get the results uploaded to this topic.

[valhalla]

I am unsubscribed from AD at the moment (doesn't sound like that's a bad thing, if Guardian's experiences are anything to go by), but there's one thing I would check before anything else;

Does this engine have a separate intake throttle from the EGR valve assembly? A lot of the VAGs around that time are integrated, but there' a chance that there's another module elsewhere on the induction circuit.

Beyond that, I'd be looking for a correlation on a (genuine) MAF meter, as that is critical to this particular diagnostic, then looking for induction circuit leaks on the intercooler and hoses with a smoke-test meter or similar. A leaking exhaust manifold or blown EGR pipe will give you the same symptoms, so it would be worth pressurising the exhaust with clean air to have a listen for any whistles or blows.

If it got to the "next stage", then it's time to look very carefully at the induction manifold for broken swirl-flaps and/or stuck vacuum actuation of the same - which might mean having to strip things down a bit to get there.

A final call after all the above; valve timing..........

EDIT : I forgot to say why that would give you the boost faults. If the meter is reading low, the fuel into the engine will be "smoke limited" more than it should be, and this will bootstrap the boost pressure down during an acceleration.

The fact that the diagnostic only comes on after 5mins drive is normal - the engine cannot diagnose airflow systems unless it is all at a nominal temperature, so the engine needs to be warmed-up on coolant temperature.

[gregg]

Hey lads, i have now got fault codes up again now and vagcom has screenshotted the engine parameters at the time the fault occurree. Im not sure if i can or.how to load the pictures up to this post to make it easier to see.

As far as i can see the egr valve feeds directly from the head into the inlet air feed pipe.

Being the newer 2.0 engine it doesnt have an intercooler on it. It feeds directly from turbo to inlet manifold. There is a plastic housing bolted to turbo which has a coupke of different outlets to it. I think its a diverter valve or sonething along those lines. From what i can see the dpf splits off below turbo and feeds up into it.

[Deleted]

When you click reply you will see an "add attachment" button on the top right hand side of the screen, click that and load attachment.