Hi there! I am trying to fix my moms GX. The VSC off, VSC trac, and anti skid lights are on plus the check engine light. It’s throwing P0430 and P0420 codes. I have already changed the downstream o2 sensors, checked the MAF sensor, checked fuses, and made sure the air filter was clean. Still has not cleared. I already know the code considers it the cats but everywhere I’ve looked says that is 9/10 not the issue so I want to do everything I can before spending thousands on cats. Thank you ahead for any help!
Edit

 

Replace the gas cap (yes, seriously) and drive it for 20 or so miles in city traffic and see if they go away.

The OEM part is about $30. P/N 77300-47010

What happens is the seal degrades over time, and it leaks air, causing emissions-related codes.

Chip H.

 

hey there I tried replacing the gas cap twice already cause the first one seemed loose but it never cleared it. Sorry I didn’t put that in my original post but maybe this one isn’t sitting on it right either. My mom got it from autozone. I’ll find out what brand

 

Leaky seal on gas cap causes evap system to lose vacuum, A good cap with a evap issue can cause the same situation.

Look for a leaky hose around the evap system.

 

Given how sensitive the system is, I believe you're going to want to use an OEM cap.

Chip H.