Check engine light....which damn sensor

So my ck engine light has been on for awhile and i knew that i had a p0136 code, and when i checked the codes today i also had a p0141 and a p1135 i see that the description for the p0136 and the p0141 are both bank 1 sensor 2 and that the p01135 has bank 1 sensor 1 so i guess the question is which sensor should i go about changing the one before the converter or after the converter? any suggestions would be greatly appreciated.

 

definitely replace both the upstream and downstream together.........and get them from rockauto.com.

 

thanks for the imput, i think i'll get the both of them seeing i'm @70k...thanks

 

welcome to TW. i havent looked up the code but if its lean on bank one and two, i would look for a vacume leak or a fuel pressure problem, if its an o2 heater circuit code, it could be voltage or the sensor itself.the common misconception is hook up the diagnostic tool and Bam the computer tells you what to fix,not so. you can go through the data stream and see whats working properly and whats not.i guess im saying to make sure what the cause is before you spend money. it can be somthing as simple as a broken wire in the reference voltage circuit.this is just my 2 cents. example: truck comes in for 02 sensor rich codes on both banks. no other codes.customer spent 800 dollars on 4 o2 sensors and installed them himself.comes in pissed cuz light came right back after 1 drive cycle.hmm i looked at it .cleaned the maf sensor dried it out and no more light.

 

thanks for the imput, somewhere i read that to check the sensors that is without a diagnostic scanner that reads real time values of what the sensors are doing (i only have a code reader), that i could check the resistance between the 2 black wires on the sensor if i have a little resistance the sensor is probably good and if there is no resistance then the sensor is probably bad....i had a little resistance in the rear o2 sensor and none at all in the front o2 sensor but at this point i think i'm just gonna get both.