Please help, my daughter’s 2015 Citigo is running massively rich. I have scanned the car with VCDS and the fault code 18105 catalyst system; bank 1 P0420 00 [01100000] - efficiency below threshold intermittent - not confirmed - tested since memory clear. I have attempted to check the oxygen sensors with vcds. Please see attached clips. Can anyone tell me if these results show the oxygen sensors are ok. Any ideal what could be the problem? I am reading the results as when the car is in full throttle it’s running 25% rich?

Sorry I can’t attach the video it’s larger than 10mb. I will try a work something out

Sorry photos in wrong order, bottom picture is the start, then going to full throttle. Any advice much appreciated.

yeaaa i rather go to a dealer

and if not go to someone you trust

Hi, welcome.

18105?

Look up the error codes on Ross Tech and internet generally for possible symptoms and causes, check and cross reference your VCDS results using other diagnostics tools, which includes your senses.

If too much fuel is being added is that because too much air is getting in or is something fuel side putting too much fuel in for various possible reasons.

I see the Freeman Steve (formerly of this Parish) and others have made suggestions on Up! forum, ironic you got here from there but that's not your matter.

You can test the oxygen sensors with a multimeter. - https://www.youtube.com/@mrautoservices7354

The history, use (use, neglect) and visual and physical checks maybe important.

Edited 21 May, 20251 yr by nta16
spelling

What engine is fitted to the 2015 Citigo?

Did you get it fixed? Mine is doing the same and having no luck finding out why.