Recently installed a oil cap breather and my check engine light came on. Any ideas? It's an 06 silverado 4.8. Codes are P0171 & P0174
Thanks in advance

 

Pull the breather off and it will solve your problem. What is happening is it is allowing unmetered air to be pulled in through your PCV system, which is why it is setting codes. The only time you will want to run a breather on your truck is if you block off the PCV and run a catch can setup.

 

Thanks,

 

Yep just seen this in another thread. Check out the pcv/catch can thread lots of good info.