It really says,
     P0155  O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)

The O2 Sensor has a heater element in it that helps it keep the air/fuel
mixture within a specified range. Your code is telling you the heater
portion of the O2 sensor is not working. Since this is an emission related
problem, and the emission system is still under warranty, I'd let the dealer
take a shot at the repairs. Having said that, replacing the O2 sensor is
much the same kind of job as replacing a spark plug. You _might_ need a
special socket wrench, but it is also possible to replace this component
with an open-end wrench, or even a box-end wrench. (Obstructions within the
arc of the wrench will dictate the need for a special tool.)

Your car has a split exhaust manifold, one portion bolted to the forward 3
cylinders and the other portion bolted to the rear 3. The sensor you need is
the rear one. Both of these sensors will be in the exhaust manifold before
the CAT. You will have O2 sensors in front of the CAT and one or more after
the CAT.

Thanks Jim

Took it to my friendly neighborhood Autozone.
Code reader showed P0155.
Code in my Bentley manual:
"Heater Circuit, Bank 2, Sensor 1"
Autozone tech said check connectors, I
shouldn't be having a problem with the
O2 sensors at 37,000 miles.
Hmmm......
Joe

It is a problem somewhere with the emissions controls.  As the car is still
under warranty, take it to the dealer.

A common problem is one of the O2 sensors, but the code reader will tell
them which one and what is wrong with it.

Jim

With 37,500 miles!
Any chance that its something simple?
I just passed emissions test  a few weeks
ago. I checked the gas cap, but that was
fine. I do oil changes myself so I don't reset
the oil change indicator.(Low mileage) That
can't be it?

Joe