The wife took her 2007 XC70 (195k) to get inspected and failed to mentioned to me prior that the CEL had just gone on. The car failed.

The car has had recent PCV service, a cleaned oil pan/sump and runs nicely. Gas mileage is reasonable for use at around 22 (mostly short trips at less than 50 mph). Gas mileage pops up to 23-24 on highway. The car has a little oil leak that I am chasing, but I don't think burns much oil.
I pulled the codes with VIDA and got ECM-400C Three-way catalytic converter efficiency, bank 1, Signal too high. There are no other codes on the car.
Both oxygen sensors are giving readings and based on my research, seem to be within spec. The front is ranging from around 1 to 15 and the rear is cycling between about .16 and .99.
Anyone have any suggestions for the next level of diagnostics? The car is pretty high mileage at this point - 195k, so I guess the catalytic converter could be toast, although this does not seem to be a common failure.