My mom has an all stock 132k mile 98 neon. Nothing changed from stock at all. Recently the service light came on, and had a code of P0138 (high volts, bank 1 sensor 2). So, with the mileage on the car and the 02 sensor never being changed, i went out and replaced the 2nd sensor per the code (after the cat). Replaced that, erased the code with my scanner and after a day it came back on....erased again, came back on immediately. What gives now, its still throwing the same code. Where should i look now....surely this is a common problem? Thanks for any and all help . My first post!
brian

 

Hmm, try replacing the O2 sensor at the headers.. I think Bank 1 is the first one.. though I am not positive...

Also, try to get it pinned ASAP since your CAT is probably suffering due to the bad O2 sensors..

 

yah i thought about replacing the first one as well..but i dont want to throw more money at something if its not going to change it.....it says bank 1 sensor 2...thats why i didnt replace the one at the headers. Yah im trying to get this handled asap as of course my mom is due for smog test. Put it on at work, and it still passes with flying colors, just has the service engine light, so it wont pass visual.
brian

 

Usually the O2 sensor that is in the header is the one that goes bad, so most likely that one is your prob, and if that still doesn't solve the problem you could have a short somewhere preventing the signal to be sent. or one of the O2 wires could have gotten burned some how like mine did ( O2 wire clip was broke and hung for a whle and occasionally touched the header) and when and if you do buy the O2 sensor(s) don't buy bosch hope some of that helps and good luck !!

 

Just for clarification, if it's stock then it's the exhaust manifold...not a header.

 

yeah, sorry about that , I was thinking about my car for sec