My niece has a 2007 Aspen and it is leaking oil and the oil is going into the air filter. What is causing this to happen?

 

You need to find the source of the oil leak first. Are you getting any codes? I'd start with replacing the PCV valve. Only around $20 for the part and easy to replace. If that doesn't take care of it, it could be more serious. Check this article for more info: https://www.carparts.com/blog/why-is...nd-air-intake/

 

Code 429 is the code it showed, What does that code mean?

 

Think you are missing some of that code. All codes start with a letter (P-power codes, B-body codes, U-network codes, C-chassis codes) and then a 4 digit number or letter combo. example P0357, B1292, B146A.

Closest I can find to "429" is a U0429 which is for steering wheel control module which would have no relation to your oil in the filter issue.

 

On top of the oil filer there is a tube connected to it. That comes from the engine crankcase through the PCV valve. It recycles exhaust and oil vapors to the air filter. Designed that way to reduce emissions.
If you do a lot of short trips or heavy city driving oil will be more prevalent at the air filter. It's probably a good thing as alternatively it could block the PCV valve and that would be an issue.
If the valve (PCV) is not working properly, you will have oil leaks from the crankcase and possibly also the upper engine body.
What do you mean by leaking? on the ground or large deposits on the oil filter?