I purchased this 2007 Jeep Commander and shortly after I got it the transmission went into limp mode and stuck in 4th Gear. I get the check engine light and I am showing the following codes: P0882, P0846, P0871, P0988, and P0876. I checked the transmission fluid and the light color of brown tells me it is ready to be changed. The Commander has 188,000 miles on it and has a HEMI and is 2WD. What is the first thing I should check?