Q: Check engine

Both codes refer to the oxygen sensor that is to the rear of the catalytic converter. With regard to Code P0037, if the rear oxygen sensor is brand new, you should check the heater circuit ground (the oxygen sensor has an internal resistance heater) and the wiring harness to the sensor as well as the sensor terminal plug. Such a check includes testing for ANY voltage drops. With regard to Code P0137, check for exhaust leaks to or around the same rear sensor as such leaks could admit oxygen which causes the oxygen sensor to output too low of a signal voltage which the ECM then sees as "out of range". If there are no exhaust leaks affecting the rear sensor, this code is caused by a wiring defect. To resolve something like this, the recommended service is a check engine light diagnostic. The fault will be identified, explained to your satisfaction and the mechanic will let you know of the cost to repair. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.