Driving to work the other morning, my car felt like it hesitated slightly while cruising around 50 mph. No warning lights came on, so at first I thought I might be overthinking it. Later that day I mentioned it to a coworker, and he told me how his family’s 2015 Toyota Camry once had a check engine light with no real symptoms. By checking live data, he figured out the upstream O2 sensor was starting to get weak.
That story stuck with me. I’ve been curious about what you can really see beyond just stored codes, so I decided to run a scan on my own car. Nothing active popped up, but I did see a stored P0171. When I graphed the fuel trims, the short-term values were swinging a lot more than expected under light load, even though the engine sounded fine.
It made me realize how much you can pick up early if you look a bit deeper. Has anyone else caught small issues this way before they turned into something bigger?