I briefly mentioned this in a seperate thread (http://www.smartcarofamerica.com/forums/f25/coolant-loss-dilemma-44388/index25.html#post521150) after I had completed an engine swap. Tonight however, I was changing the oil in my other smart car and checked the same wire harness for damage. Guess what I found??? You got it! Wire harness damage where the upstream O2 sensor wire harness and the air injection pump hose cross each other. They've been rubbing together causing wear into the wiring harness. I sealed off the exposed wire and reinforced that part of the harness with plastic wire loom.
Air Injection Pump Hose
Pull the Air Injection Pump Hose back and inspect the wire harness below it.
Both my cars have 50K miles and both had this damage.
Air Injection Pump Hose

Pull the Air Injection Pump Hose back and inspect the wire harness below it.

Both my cars have 50K miles and both had this damage.