I was driving to work the other day, and my check engine light came on. A buddy of mine has a code scanner, and it came back as the P0141 code. I cleared the code and the light went off. A few days later, the light came back on. I know that there are more than one sensor, and have checked out the prices through a different places, and they list sensors either upstream or downstream. I really do not know what the difference is between the two? Also, with this code, where would the sensor be located at? Any help that anyone can give me will be greatly appreciated. Thanks in advance...

 

with O2 codes it will usually tell you a bank and a sensor number

Heated Oxygen Sensor (Bank 1 Sensor 2) Heater Circuit Malfunction

to figure out which side is bank 1, you need to find cylinder number 1 which on these trucks is located at the front driver side of the engine. and sensor 2 is the second sensor from the engine.

so basically its going to be driverside and the one after the cat converter

upstream and downstream just refers to the location in reference to the converter. so downstream would be downstream of the converter