2004 Jeep Liberty Trail Rated - PO137 and PO138 OBD2 Codes Explained & How to Fix

I own a 2004 Jeep Liberty Trail Rated and recently noticed the check engine light came on. It would stay on for a while, then turn off, and later come back on intermittently. After having it scanned, I received two diagnostic trouble codes: PO137 and PO138. I'm not familiar with what these codes mean or how to fix them. Previously, my vehicle had an engine stall issue that led me to replace the engine due to a check engine light — so I was hopeful this wouldn't happen again. However, I'm now concerned about potential underlying issues. Can anyone provide clarity on what PO137 and PO138 indicate and what steps I should take? Additionally, after experiencing a flat tire, I used my spare. Now I’m looking to replace the tires with Goodyear Wrangler-style ones for my Jeep. I noticed that different bolt sizes are available — how do I know which size to use? My current tire is labeled P225/75R16, Goodyear Wrangler, 104S Standard Load. Where can I find this exact tire without overspending? Thanks in advance for any help or guidance.