hello, the most common problem that causes this is a bad o2 sensor. i am having some trouble getting the flow chart on here though.
here is a wiring diagram to help you out with some things to check first. the typical o2 sensor runs in the area of 70-125 dollars.as the diagram shows youll want to check fuse k first .
p0037 refers to the downstream oxygen sensor it is mounted in the exhause pipe after the catalytic convertor.
the sensor your lookin at is 1/2 in the picture