I have two codes on my 2003 Mazda Protege5: P0037 (HO2S Heater Control Circuit Low (Bank 1 Sensor 2) and P0090 Fuel Pressure Regulator Control Circuit.

My car is fine and no problem is seen, still daily driving. I got the code cleared by a mechanic before because he said the HO2S isn't that important for where its malfunctioning, and that P0090 indicated that the fuel pressure wire was removed at one time (it is now reconnected, my cousin was trying to show me how to prevent car from being stolen by disconnecting that wire so if people steal my car they won't be able to start engine). After the code was cleared, the check engine light came back on with the same codes.

I'm not sure how I should go about fixing this. Someone help please? appreciate it

 

The heated oxygen sensor is heated so it will reach operating temperature much faster than a non heated oxygen sensor. The computer will be able to use the sensor data earlier and run more efficient earlier after a cold start. There are 2 ways the heater circuit can malfunction: the inner circuit, meaning the heating element inside the HO2 sensor may be busted: replace the sensor. Or: the wires that go to the heater element may be interrupted somewhere. Check the connections at the HO2 sensor, follow the wires to see if they have shorted out somewhere, check the connection to the PCM.
Follow a similar approach to the Fuel Pressure regulator circuit. the regulator may be bad or the wire going to it may be faulty.


After checking and possibly fixing the problems erase the CEL: To clear the code remove the battery negative and then step on the brake pedal to drain any remaining voltage from the computer's memory.
If the codes return you still have not fixed it.