[John_E]

Various vendors show two different Bosch part number series:

16132 (eqiv: 16257 / 16305 / 16109)

and

16978 (equiv: 16121 / 16307 / 16161)

Which is correct -- or preferable -- for the downstream oxygen sensor on an AUG (probably AWM, as well) 1.8T?

Does anyone know the difference? Lead length, perhaps? (I did read a few complaints from customers who said the leads were too long.)


I am getting no codes, but failure of cat test readiness to set after several days of driving, including at least a couple of 30-minute+ freeway trips. I replaced the front O2 sensor a few years ago and would not be surprised if the rear were shot by now. I **believe** this could affect my readiness setting, without throwing a CEL.

 

[FrescoGreen01.5]

The Bosch web site shows 16978:

https://www.boschautoparts.com/en/auto

 

[John_E]

The Bosch web site shows 16978:

https://www.boschautoparts.com/en/auto

Thank you, FrescoGreen. Fortunately, my catalyst ready monitor finally cleared yesterday after a 90-mile round trip, and the car passed smog today.

 

[Tomvw]

Good to see that you got it sorted.
If there was a fault that would prevent readiness from resetting, it would set a fault code.

 

[John_E]

Good to see that you got it sorted.
If there was a fault that would prevent readiness from resetting, it would set a fault code.

In addition to the MIL/CEL, my elder son's 2002 A4 has a dash-mounted EPC lamp, which seems to illuminate on "low catalyst efficiency," according to my VCDS. It does not come on very often, but I should probably do a full scan of fuel trim, etc., and make sure his O2 sensors and MAFS are up to snuff before he comes due for his next smog inspection.