SCR system diagnostics with VCDS

I got countdown to doom counter (" no engine restart possible after X km)” on Seat Alhambra 4motion TDI 2.0, year 2014. This counter cannot be reset, nor cleared with regular after maker codereaders, or VCDS. My car has visited so many workshops now, that it looks like, most workshops don’t have very good skills on troubleshooting these issues. Historically car visited VAG-service 3 times after deer crash, then couple of other workshops due DPF and cat isues, and I am getting fed up, so I would get this fixed myself.

The current acute fault is due some workshop removing the old blocked catalysator cells. Without going int the details why they did it, I would like dig into the issues of fixing this without SCR delete. I would like keep the in the car in original shape. However, the VAG stealership price for new catalysator was over 2 k€. Price is quite ridiculous, when regular catalysator cell costs about 20 euros. I cannot figure out how SCR-catalysator cell coating would be different.

After fair amount time for research I found a aftermarket catalysator from goodcat.nl.
I was expecting that I could see some SCR measurement values with VCDS, before I start the job.

I attempted yesterday to look NOX values yesterday with VCDS.
Extracting from log files - most values read seem to read zero:

TIME STAMP 0,75 2,25 3,75 5,25 6,75 20,24 21,75 23,25
Loc. IDE03768 NOx sensor 1: feed voltage mV 0 0 0 0 0 0 0 0

TIME STAMP 1,24 2,75 4,24 5,74 7,24 20,76 22,24 23,75
Loc. IDE05346 NOx emission NOx sensor 2 ppm 0 0 0 0 0 0 0 0

It this a failure on VCDS, or is this due the fact, that SCR/NOX system is not active ?

Most of other SCR parameters give the value “unknown” (like SCR inducem system status XXX). There multiple rows for “SCR inducem system status-NOX emissions too high” (ENG110382…)

I could not locate any material on SCR-system diagnostics, so it would e great If could put to together some. I looking for straightforward instructions for using VCDS to troubleshoot th SCR issues.

There is pretty good paper by (ANDRÉ ÅKERBERG DANIEL TÖRNROOS) on troubleshooting the SCR-systems here, although is for Scania systems - http://www.diva-portal.se/smash/get/diva2:695223/FULLTEXT01.pdf

Can I find some assistance here ?

... start with posting a complete unedited Autoscan... after that you maybe get some answers...

thanks for the reply, I managed to get some measurement after SCR Lock release, and running SCR efficiency test for NOX sensor 2.

After scr lock release, "pre-glow engine light" started blinking.

Need to press brake and gas pedals, like reported in other threads, and as instructed in VCDS UI.

Test ended up to with "aborted for security reasons | error", with any explanations why. I was not able to immediately restart the test- I guess that pipe should be interpreted as "OR". Although it not very intuitive, because in the beginning I was not able to get test started at all - you almost immediatelly ended up with error message. Once I receive the catalysator, I will play more.

This still looks like rain dance to me, since most of the SCR measurement values, including NOX sensor read zeros, and there no explanation for reason of test failure. I will try keep you posted with autoscans later.

Also, SCR test seems to really only start after exhaust gas temperature reaches point, which is over 400 degrees. There was clear change in change RPM that point. Voltage measurements on my previous post never changed from 0 to anywhere. . I've got measrement logs in different machine, so will post them later.

bitwise: Hi. hmm............ your background observations are interesting, but without a context of an unedited, complete auto-scan of the car - it's all academic !!!

To repeat :

Mari said:

... start with posting a complete unedited Autoscan... after that you maybe get some answers...

Click to expand...