so my mil light is on and the 2 codes are p0140 and p0138... p0140 says O2 sensor bank 1 sensor 2 no activity and p0138 says O2 sensor bank 1 sensor 2 high voltage... now in my mind no activity means not plugged in or not working... weird thing is these codes come and go, completely randomly... any help will be great... i do have aftermarket exhaust and i think downpipe as well (on the car when i bought it)

 

is it a catless d/p with no tune to compensate for it?

 

possibly...i bought the car from a dealer with the mods done so not sure...is there anyway to tell??? when i bought it there was no cat but due to Pa laws there must be one so that could be it

 

clogged cat would be my guess if you have one on it.
any loss of power, air hissing sounds.
if not then possibly shot 02 sensors.
what kind of car?
im in york like 4 days a week haha.

 

06 cobalt ss/sc... cat is 1 year old

 

hmm. well any loss of power that you notice.
registering any higher than normal boost levels?

 

not really... i did at one point but it was a bad MAF... fixed that and everything was good... if i remember right p0138 was on at that time as well but when i swapped the MAF and reset the cpu it went away... think it might need tuned since it didnt have a cat before i bought it???

 

nah bc with catless you just delete the 1 check engine light that comes on because the 2nd 02 sensor reads the same as the first.
if your cats not clogged i'd say it's bad o2 sensors. guy mightve been running rich or something and killed them.
where you at in york i have HPTuners

 

actually i live in Loganville...bout 10 mins from the Maryland bolder... where are you at???

 

im in hanover like 30 40 minutes below york bout same distance from md lol. no clue where loganville is tho.
if u jack up ur car you can see on the catback is the one 02 sensor i'd go under, wd40 that, and then undo it and see how bad it looks. maybe even test for electric current to it.

 

what is an HPTuner.... im kinda new to all of this...damn noob questions!!! lol

 

hptuners is the program 99% of us use to tune the car with. you can also scan and datalog with it too.

 

really...what would it take to possibly get you to tune it??? does that also allow you to change things in the cpu with tire size??? and i am willing to drive mainly bc of the sonic!!!! lol

 

i'll be honest im not near ready to start tuning others YET we can meet up some night and i can see what all is on your car at the moment though, injectors/pulley/i can even log and pull your tune off of your car without having to charge credits to see whats up too.