I don't own a Chevy, but I'm trying to help an elderly neighbor with an '05 Tahoe. She took it to the dealership for an oil change, and while there they told her she had a defective "oil sensor for the engine", and they wanted her to come back in so they could run a $179 diagnostic test to see what the issue is. She's never had the oil light come on, nor CEL, and I didn't see any codes when I used my cheapie reader. What sensor does this vehicle have, other than the normal pressure sensor that goes to the gauge or idiot light? If it's just this they're talking about, why would they run a $179 test on a $50 part? I'm smelling a scam... if there's really a problem with the unit, I'm guessing I can swap it out for her myself and save her a lot of dough. Thanks for any help!