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Hello, Finally got this Beetle on the road and driving great. It passed inspection with all readiness monitors set and no issues. Then all of a sudden the CEL comes on. Code is P0420 which is most likely the o2 sensor after the cat or the cat itself.

But...

I don't think the air pump is working properly or possibly at all... Sometimes at startup theres a brief 2 second noise that kind of sounds like a plastic fan blade getting stuck or a drill bit getting stuck type of sound... It doesn't seem to be vibrating or making any noise while the car is running. The rubber pump mounts are also broken and the previous owner has it held in place with zip ties. It looks like an extremely easy fix after all I've been through with it.

Can this be the problem or should I be looking at the cat?
 

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16804/P0420/001056 - Ross-Tech Wiki

A wide range of possibilities on that trouble code; testing and inspections, need to be done to diagnose the problem. Look at the list of possibilities; you have your troubleshooting and testing, work cut out for you!

The secondary air injection air pumps; do wear out and die. You could go through a process of testing it and see if it is working, audible grinding sounds could indicate it has failed. When you remove the air pump; to replace the rubber mounts, you could hook it up to your battery and see if it comes on. They tend to be pretty loud but shouldn't have grinding noises and air should flow out of it. Also, check for air coming out of the seam of the pump body; some early models, had rivets that would fail and the pump would come apart. There are some diy's for fixing this issue.

This is not shown; for a New Beetle but once the pump is out, the repairs are the same:

http://uk-mkivs.net/topic/9315-step...pairing-the-secondary-air-pump-with-pictures/

The air pump mounts; fail ALL the time, the rubber just falls apart! DORMAN makes a affordable aftermarket kit and it is something you can do yourself. Here is a video showing the repair:

https://www.youtube.com/watch?v=Svr55m9tHs8

Dorman Products - 911-926

DORMAN PART # 911-926

Air Pump Mount 3 PCS
Application Summary: Volkswagen 2006-98


Application Notes:
L4 1.8L (1781cc)
L4 121 2.0L (1984cc)


Dorman parts are available from most auto parts stores; like orielly's and autozone, amazon typically has great prices on Dorman products.
 

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You may have issues with the secondary air, but I don't think I've heard of a bad pump causing the P0420 code. P0411 will usually pop up when you have SAI issues.

I would see if you can get ahold of a scanner that will take a look at the operation of your O2 sensors and see if you can tell how they are performing.
 
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