but you don't know what caused it. a previous owner may have done some "tweaking" that lead to a failure. just like construction, code books are there for a reason, to ensure that the installation is done correctly and keep homes from burning to the ground. new vehicles are extremely complicated. even the wrong spark plug can make an engine miss, or not start at all. the electronic ignition reads resistance across the plug, which even though the champion plug is the exact same plug as an AC plug, the resistance is different causing the ignition to read an error which will put it into a limp mode. While I’m talking about spark plugs, I picked up 15 HP while dyno tuning a 406 CID small block chevy last year by increasing the gap to .045 from .035. from 605 hp to 620 hp. I wouldn’t have believed it, or even tried it if I didn’t feel like experimenting. But the point I’m trying to make, is that engines are not as simple as they were 20 years ago. A very small “tweak” can lead to very significant changes, both pro and con.
