2019 Lexus GS — catalyst efficiency code but car drives normally

It did catalyst efficiency code but car drives normally twice this week, both times after sitting. No change in mileage feel. No warning lights, which is why I'm documenting it.

This is usually cheaper to test than to guess. Two 2019 Lexus GSs can feel identical and have different causes, so measure before you copy someone else's repair. You'll know quickly if you're on the wrong tree. I'd want that in writing, not as a promise. Make the next action something you can finish this week. Not interested in a five-hour wait for a shrug.

Log the conditions before you spend. Loaded-suspension checks on the 2019 Lexus GS catch play that a wheels-hanging inspection misses. Don't erase codes until someone who can help has seen them. On “catalyst efficiency code but car drives normally,” that was the fork that mattered for me. Have you gotten a second quote in writing? This is me being the wet blanket on purpose.

Start with the test that can prove you wrong. Move a coil or plug on the 2019 Lexus GS if it's cylinder-specific and see whether the code follows. Don't erase codes until someone who can help has seen them. Happy to compare notes if your setup is different. Worth doing even if the car feels fine right now. I'm keeping receipts and dates in one folder.

This is usually cheaper to test than to guess. Swap the cheap/easy piece first on the 2019 Lexus GS and see if the fault moves. Save the big job until that test fails. Verbal 'we'll take care of it' is not a plan. Trying not to diagnose from the couch.