I know.... everybody says that (always, it seems) but there are, in fact, times when it's appropriate.
Only because it's relevant; Took my Pathfinder to my local tech; "Turbine Speed Sensor in Tranny is bad"
Still under warranty so I bring to Nissan. "Nope- it's the _______"
"OK, well can you please just have the tech double-check that the sensor is ok because...." (I'm always nice- never arrogant or a smart-ass).
All that request would have involved was their tech feeling the top of the tranny (where the sensor is) and seeing it was wet with fluid.
"NO!" was their response.
They "fix" the tranny and, of course, there's a puddle under the car the next morning.
I bring it back. Wonder of wonders.... It's the sensor. Imagine that.
Good luck, take no $hit and keep us updated.