Recently bought a WRX, the O2 sensor went bad, the shop I normally use didn't want to mess with it so I went to the dealership. While I was waiting I get a text saying my car needs $8,000 worth of work, I just bought the thing so I am starting to panic, the advisor said the battery sensing plug was messed up and to fix it the ENTIRE engine harness had to be replaced. I asked to see what they were talking about, so we walked into the shop, it was a small plastic plug about the size of my pinky finger the previous owner had wrapped in electrical tape so i asked if we can just wrap it back up, the mechanic shrugs but wraps it back, that was 2 years ago still never had an issue even though the advisor was like you need to get this fixed sooner rather than later. Never went back.

Older BMW and Mercedes. The plastic in the engine bay turns into expensive RNG repair add ons as you take it apart. Audi too really