What is P0037?
P0037 is a generic OBD-II diagnostic trouble code (DTC) defined as “Oxygen Sensor Rear Heater Control Circuit Low (Bank 1 Sensor 2).”
For an engine to run efficiently, it needs the correct air-to-fuel ratio. Your vehicle’s powertrain control module (PCM) or engine control module (ECM) ensures that the proper balance of fuel and air is being pumped into the engine.
The powertrain control module or engine control module measures these ratios correctly with the help of sensors placed around the engine. Some of these sensors are oxygen sensors (O2 sensors).
There is one oxygen sensor before the catalytic converter (known as oxygen sensor 1) and another after the catalytic converter (known as oxygen sensor 2). Bank 1 refers to the side of the engine where cylinder one is located. In a 4-cylinder engine, for example, there is only one bank (bank 1).
These sensors give feedback to the powertrain control module on any adjustments that need to be made to the air-to-fuel ratio.
A P0037 code links directly to oxygen sensor 2 on bank 1. For this sensor to give accurate readings, it needs to heat up. To do this, a heating wire (also called a heater element) is placed inside the sensor, quickly heating it to the proper working temperature.
If the PCM detects an irregular voltage measurement from oxygen sensor 2’s heater element, it stores the P0037 code.
In other words, the bank 1 sensor 2 is not receiving the correct battery voltage (0.1V – 0.9V) to reach working temperature and is malfunctioning.