I have a 2004 Mazda 6. My check engine light is on, with a code P0171. I know there can be many issues that cause this code and plan on getting a diagnostic test done. I am hoping if I explain my issues I am having someone can pinpoint my issues. I car is losing alot of power. It is accelerating a lot slower than it used to, and hesitates very slightly whenever I shift gears (its a automatic). The biggest issue I am having tho is that my car some times will not shift into 4th gear. It will just stay out of gear. If I give is a few seconds (quicker if I release the gas) it will pop into gear, violently if I am at a high rpm. This issue started with this code, and has continuously gotten worse. Any idea what could be causing this in connection with a P0171 error?

 

When was the last time the transmission fluid was changed?

 

Actually I havent. The T-fluid is a little brown so I will change it this evening. I have never changed transmission fluid myself but it seems pretty simple. Instead of taking off my pan would it be okay to just take off a hose to drain my T-fluid? If so, which hose should I remove?