Hey, i sure this has been discussed many times, but how many o2 sensors does the 1.8T engine have? From what I have gathered since it only has 1 bank of cylinders it has 2 sensors, 1 pre and 1 post cat. Let me know is that is incorrect. i have pulled a 17521 code which I think is the pre-cat sensor, if you could confirm or deny this I would really appreciate it. the CEL light is not on, but the code is looming. Also have any of you had good luck with universal o2 sensors or should i stick with a direct oe replacement? i have also heard it is better to replace all o2 sensors at once, but i dont know if that has any merit. Thank you very much

 

2 sensors, pre and post. Just make sure you get the correct sensor for your engine code. The universals work just fine, they are the same thing as the specific ones, just dont have the connector. Its a good way to save $50.

You dont have to change both, only reason i see doing both is since you are in there... but i dont usually replace whats not broken and not a hassle to replace.

If you dont have a constant cel, you probably dont have a bad o2. Better chance of a blown gasket. The turbo the manifold ones suck and blow often. Most run w/o them so check for leaks in the exhaust system

 

I cleared the code and it came back right away, but the CEL has not come on once. Which gasket were you referring to? Is it something I should be concerned it? The way you described it sounds like its a common failure. Thanks again Cincy.

 

THe gasket the goes between the turbo manifold and the turbo. A leak pre-o2 can set off a code. Easiest way to tell for a leak is to start a cold car and feel around before it gets hot.

 

If indeed there is a leak there is it something I should worry about? Also since the code is there but the CEL is not on, is there different levels of o2 malfunctions? At what point would this code trigger the CEL? thanks

 

Its something that needs fixed. A bad o2 and a leaky exhaust can cause different codes. The light can take up to a few days to turn on

 

The code has been there over a month and driven over a 1,000 miles. If must not be malfunctioning enough to trigger the cel? does the cel take in consideration different levels of malfunctions or is just working or not working?

 

I put on a new catted 42dd downpipe (with new gasket) about a month ago with o2 spacer on the 2nd O2 sensor, and I did an autoscan and found this :

VCDS-Lite Version: Release 1.0
Sunday, 15 July 2012, 15:07:36:0


Chassis Type: 8N - Audi TT
Scan: 01,02,03,08,15,17,22,35,37,45,55,56,76,77

-------------------------------------------------------------------------------
Address 01: Engine Labels: 06A-906-032-AMU.LBL
Controller: 8N0 906 018 K
Component: 1.8L R4/5VT G *0003
Coding: 06710
Shop #: WSC 79415
TRUWT28N511011364 AUZ5Z0Y7303282
2 Faults Found:
17521 - Oxygen (Lambda) Sensor; B1 S1: Internal Resistance too High
P1113 -- 35-10 - - - Intermittent
16525 - Oxygen (Lambda) Sensor B1 S2; Heating Circuit: Malfunction
P0141 -- 35-10 - - - Intermittent
Readiness: 0000 0000

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: Redir Fail!
Controller: 8N0 907 379 E
Component: ESP 20 CAN V005
Coding: 18446
Shop #: WSC 01236
No fault code found.

_______________________________________


Do you think it could be the sensor(s) or maybe a leak in the downpipe ??

also, I did a log with vag-com and Have ALOT of timing pull right around 5000rpms

Thx

 

I got a code for O2 sensors. Checked the cat converter and it was fine. Replaced the o2 sensors with some from Walker instead of the Bosch. It solved my issue. I have the 3.2 litre which has 2 pairs of sensors.