2018 Cadillac CTS-V — catalyst efficiency code but car drives normally

This is usually cheaper to test than to guess. Swap the cheap/easy piece first on the 2018 Cadillac CTS-V and see if the fault moves. That's the branch I'd chase this week. I'd want a dollar figure or a measured spec, not 'should be fine.' Cold start is when I can actually reproduce it.

Checked the easy stuff on the 2018 Cadillac CTS-V and found one clue worth chasing before I book a shop. I'll poke at it this weekend.

I'd want a measurement, not a hunch. Swap the cheap/easy piece first on the 2018 Cadillac CTS-V and see if the fault moves. That's the branch I'd chase this week. I'd want that in writing, not as a promise. Heat soak after errands is the other window.

This is usually cheaper to test than to guess. Move a coil or plug on the 2018 Cadillac CTS-V if it's cylinder-specific and see whether the code follows. You'll know quickly if you're on the wrong tree. Have you gotten a second quote in writing? Cold start is when I can actually reproduce it.