Polo Q - How do you Perform Oxygen Sensor Aging Check amongst others?

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Polo Q - How do you Perform Oxygen Sensor Aging Check amongst others?

Post by janski » Sun Jul 02, 2017 3:27 pm

Tried a Polo forum and alas, no reply!!!!

Sooooo, I thought I'd try you knowledgeable lovely peeps.

FYI - 2002 9n 1.2 12v AZQ

VAGCOM throws up ...

16804/P0420/001056 - Catalyst System; Bank 1: Efficiency Below Threshold

Ross-Tech suggest the below.

Possible Causes
Leakage in Intake and/or Exhaust System
Catalyst faulty
Oxygen Sensor(s) faulty
Oxygen Sensor(s) Control faulty

Possible Solutions
Check Intake and Exhaust System for Leaks
Check Catalyst
Check Oxygen Sensor(s)
Check Oxygen Sensor(s) Control
Perform Oxygen Sensor(s) Aging Check

Found this on line for checking the above, but for another VW i.e. a MKIV VR6 Golf/Jetta....


Just wondering if anyone knows the relevant checks for the blocks and values in the "Engine" control module with VAG-COM? And which
/what is Bank 1? I understand there is a sensor before and after the catalyst, so I presume the 'Bank 1' refers to one of the sensors? Or am I barking up the wrong tree?


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Re: Polo Q - How do you Perform Oxygen Sensor Aging Check amongst others?

Post by Albrown » Sat Sep 09, 2017 3:38 pm

Bank one refers to one side of a v engine, straight 4 only has bank one if that makes sense.
Cat efficiency code means the sensor after the cat is not giving the expected reading and it could be the cat isn't working correctly anymore or a sensor fault or as you said, a leak in the system.
I don't know the blocks to check, but the important one is the pre-cat sensor as it is the one that runs the fueling, the post cat one only checks the cat efficiency. If the car is passing the emissions test then it's often easier to just leave it alone. It could be the post cat sensor needs changing but it could be the cat (a cat that passes the emissions test fine can be worn enough to put up a code). Depends how much the light bothered you and what you want to spend, but there are adapters that help to fool the post cat sensor and keep the light out.

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