I need to know which O2 sensor heater to change out?the error code was PO141, i dont know what side it is tho?

SHOULD SAY EITHER UP STEAM OR DOWN STREAM ON THE COMPUTER. UP STRAM IS RIGHT SIDE AND DOWN IS LEFT SIDE

Hi, this is sensor 2, which is the downstream sensor screwed into the exhaust pipe behind the catalytic converter.

P0141 - O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
This code means that the heated circuit in the oxygen sensor on bank 1 decreases time needed to enter closed loop. As the O2 heater reaches operating temperature, the oxygen sensor responds by switching according to oxygen content of the exhaust surrounding it. The ECM tracks how long it takes for the oxygen sensor to begin switching. It the ECM determines (based on coolant temp) that too much time elapsed before the oxygen sensor began operating properly, it will set P0141. See also: P0135 (Bank 1, Sensor 1).

Symptoms: You will likely notice poor fuel economy the illumination of the Check Engine Light.

Causes: A code P0141 may mean that one or more of the following has happened:
open or short to ground in the wiring harness
O2 heater circuit wiring high resistance
O2 heater element resistance is high
Internal short or open in the heater element

Note: Typically a failed catalytic converter does not cause this code. You're more likely to see a P0420 code for a failed converter.

Possible Solutions:
Replace oxygen sensor (cannot repair open or short that occurs internally to sensor)
Repair short or open or high resistance in wiring harness or harness connectors



Also, culd check THIS LINK.

Hope this helps.