Recently, I had P1143 pop up which is Heated O2 Sensor 1, was told it was the passenger side O2 pre-cat sensor so I replaced it.. reset the code.

After 15-20 min of driving, Check Engine light is back and produced:

P1134: Heated Oxygen Sensor 1 Lean Shift Monitoring (Bank 1)
P1163: Heated Oxygen Sensor 1 Lean Shift Monitoring (Bank 2)

Anyone give me insight on what this means?

Sounds like a bad/dirty MAF sensor. I'd double check your grounds (on the passenger's side of the intake plenum, coming out of the wiring harness) by loosening them and tightening them again. Don't strip the bolts! Do both of them, they're next to each other.

Then clean your MAF sensor out, as it sounds like it's reading incorrectly. If that doesn't do it, let me know, and we can figure something out locally. I can take a look at it for you, since I'm in Denver.

Where's the MAF located?

I'll check the grounds tomorrow. I gotta clean the positive battery terminal while I'm at it.. so corroded.

It's right after the airbox. It's bolted to your upper airbox lid with 4 bolts. Be carefull with it. Clean it gently and make sure it's cold when you do it.

That may be a possible culprit.

Considering I just changed one of the O2 sensors.. and reset the codes.. now both going at the same time, seriously doubting the problem is with the sensors and hopefully its the MAF sensor needing some cleaning.

Hello, I have the same problem with these codes appearing right now. Did doing the MAF and grounds work? Please let me know.