2018 Cadillac CTS-V — coolant is old by age but mileage is low

Ask what changed right before it started. Write temp, speed, and in-gear vs coast when the 2018 Cadillac CTS-V does it — then decide on parts. Don't erase codes until someone who can help has seen them. I'd want a dollar figure or a measured spec, not 'should be fine.' If it repeats twice more I'll book time.

Intermittent stuff lies if you only catch it once. 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. On “v — coolant is old by age,” that was the fork that mattered for me. This is from a 2018 Cadillac CTS-V in Salt Lake City. Happy to compare notes if your setup is different. If that fails I'll eat the diagnostic fee.

Log the conditions before you spend. 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. On “v — coolant is old by age,” that was the fork that mattered for me. Happy to compare notes if your setup is different. If your situation is the opposite, ignore me. Trying not to diagnose from the couch.

If it were in my driveway, get a real battery/charging test on the 2018 Cadillac CTS-V, not just resting voltage, before blaming a module. Save the big job until that test fails. Happy to compare notes if your setup is different. Not driving it hard until I know more.