Adblu system fault no restart 650 miles!!!

[liam walsh]

Hi All.

2014 A4 2.0 tdi Ultra CNHC engine.

Adblu system fault displayed in yellow with spanner. 650 miles to no start. ( now 200 miles)

No fault codes logged read on my VCDS and Audi dealer reader . Car is driving 100% perfect.

Adblu full and reading full on VCDS.

With engine running:
SCR system pressure 5000hpa
Adblu pump activation 50% .
Adblu pump rpm 1600

I've done scr lock reset and associated but no fix.

Adblu injector metering test carried out with injector out of DPF can hear it cycling as it should and squirting out two jets of adblu . Total adblu dispensed during test very close to 25ml for a 2.0tdi I've read that's about right.

Removed adblu pipe from injector while engine running , adblu comes out but not a steady stream it seems to spit out and have alot of air in the line too .
Is it normal to have air in the adblu line and if not what could cause it seeing as I have the required 5000hpa pressure? Although seeing as the injector test was satisfactory I think the adblu supply is good.

No leaks and there is about 85psi at 5000hpa so if there was a leak I'd know about it.

Nox sensor in DPF cleaned with heat eventhough no faults I though it couldn't hurt.

Had car with Audi three days ago for software update to try rectify the issue. I drove it 100 miles after the update and the fault remains.

Anyone experiencing similar issues or can provide any guidance to rectify the issue. I'm running out of miles seeing as it takes a 50 mile drive to clear the light once you fix the issue.

[Crasher]

No I haven’t seen that... worrying one.

[liam walsh]

Looks like I'm doomed to suffer the dealers parts and labour rates.

[Crasher]

There is a known issue with the reductant metering lines on cars built before 17th February 2014, private message me the REG number. The injector has been revised as well but it is £426! Looking deeper into this I need to be at work but there are a LOT of revised parts.

[liam walsh]

You have PM crashers.

Build date 10/14 . Regarding the injector it passes the metering test you would hope it's ok . Everything in that adblu system is a ridiculous price from the tank to the pump to the nox sensor. You could rack up 2k in parts and labour without a problem. For a 6k car that's a hard to justify.

[Crasher]

As you say, built 28/10/14 so the updated parts that could be relevant are

1) Tank assemebly passive, one revision back
2) Transfer pump one revision back
3) Tank assembly active, three revisions back
4) Delevery unit one revision back
5) Control unit one revision back with a TPI and software version management code
6) Metering line for injector, complete redsign
7) Injector, at least two revisions

To buy and install all the parts which have been upgraded to their current versions would cost at least £3K, possibly more.

That is about as far as I can see at home on my iPad. Frankly the sceptical engineer in me would say the early versions of this system were a disaster. You can try the crossed terminals trick, I am normally derisory about this but I have had it work for me on Golf 5 central convenience systems when they shut down the cars left doors.

It could be worth spending 7 Euro for an hour on erWin Audi looking at the field measures and TPI’s to see if there is anything interesting.

[liam walsh]

Thanks Crasher. I'm not feeling optimistic and no fault code to go on is a nightmare scenario. I tried the crossed terminals for a couple of hours but no joy. Thanks for looking. I'm booked into the ******** for Tuesday morning. I'm not sure theres much more I can do without changing out parts and nothing in that system comes cheap.

Edit who knew st.eal.ers in a swear word.

[liam walsh]

Crasher or anyone. How can I check if my A4 has a NOx21 sensor fitted . It's a nox sensor to measure nox after the dpf . I'm getting 0v, 0 nox ppm reading and 0 o² concentration after DPF and NOx21 --- reading on VCDS while engine running

[Crasher]

It has one NOX sensor, that has also been upgraded, it is in the downpipe after the DPF.

[liam walsh]

Hi Crasher . Thanks for that . I found a bit more info on that in the meantime. It has one wideband nox sensor located just after the turbo but before the adblu injector and combined catalytic converter dpf unit. So back to the search for me as there is no NOx21 sensor in my car . Pic below might help someone in the future

20200809_204052.jpg