CEL: P0138 Troubles!
 

heres the situation:

I put on a 3 inch downpipe and also a 3 inch test pipe with a QTP cutout welded in. Also with the install i used a mechanical CEL fix for the rear o2 sensor...

well right after the install my CEL wasn't on....

after about 5 days the CEL came on....

codes were: P0136 Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2) and P0139 Oxygen Sensor Circuit Slow Response (Bank 1 Sensor 2)

So i installed Scan Tech Tool so i can read my CEl's and clear them on my own and i cleared these codes pry 2 times bc the CEL is annoying...

And it was really cold and rainy out one day and i started my car and no CEL? i was confused it just went off on its own...

then about 2 days later it came back on and this time i got the P0138 code for high voltage...

I tried clearing this code but it comes back as soon as you start the car the next time...

So the other day i got under my car to look and see if the wires were exposed or anything...

The wires were fine but the sensor was rubbing against my frame so i didn't know if that was shorting it out or what? so i wraped the sensor heavily in electrical tape and restarted my battery and there was no cel....

but the next time i started my car it was on...of couse:banghead:

but then the next morning i get in my car and was driving around then i realized the CEL was off! whoa i thought i fixed it and it has stayed off for 5 days until today and its back on!

i have no clue what the deal is but it works some days and the others it don't

im really confused!!!

so what are my options? is there some kind of patch i could put on my ecu so it never reads from the rear o2 sensor bc all the rear sensor is there for is to let you know if your cat is working properly....obviously the mechanical fix isn't working that well....maybe a o2 simulator?

give me your opinions and suggestions! CEL is really annoying

Yes, look in the ecuflash forum.

I would also make sure the wires aren't ever rubbing on the frame, as it can rub through and short out and the car will blow a fuse and leave you stranded. ;)

alright cool!

there is a black rubber tube around the wires and i pulled it down so it covered all of the wires and taped that also so it wouldn't move...

razorlab....TUNE ME FOR E85!!! haha i've been lookin at your E85 tunes looks awesome! i need injectors and fuel pump tho

my CEL went off again! and today is rainy/snowy and cold....seems like the cold weather makes it go off....:crap: confusing

Maybe you need a new 02 sensor.

yeah...i think i am just gonna disable the rear o2 and take out the rear o2 and use it as a wideband down the road possibly

it might be that o2sensor might have got damaged inside since you said it was rubbing aginst the frame. eventhough it looks ok outside its possible that its got damage inside

Im having the same problem too when it gets cold it happens Did you do anything to fix the problem?

Why not just disable the test and move on? Can we search today?

this might be stupid but is scan tech tool like a code reader from say autozone?

I believe it's a program downloaded and used to clear codes with the tactrix cable for free without purchasing a real scantool

nope
have this problem too. its just the rear o2 sensor. spark plug non fouler cheater method works, but someimtes, when the car has rich running conditions it will throw the light.

its alright though, the light does not affect how the car drives. simply just a warning light. i had to put 3 non foulers on the o2 sensor to get it to go away. NOTHING is wrong with your car though.

some evos just cant get rid of the light and it comes off and on throughout season changes etc. i just deal with it since it doesnt hurt anything and nothing is wrong with the car. just save the money and hassle, do the o2 sensor non fouler cheater method in "how to" forums and move on.
{thumbup}

Sub'd... I've been getting these P0138 codes increasingly the last few months, now I get them every 10 miles/minutes of driving. I already had one anti foul extension on, I added two more, but I'm still getting the code. I may try a few more extensions (cheap) before I get a new sensor ($$$) ... if the O2 sensor has really gone bad, why did it go out? Is there something about reading the downstream exh that makes it go out sooner than the front? Or is there anything about the CEL fix that reduces its life?

Not sure if the OP ever got this sorted out?

For the P0138 I was getting, I finally put in a new rear O2 sensor (well, technically it was used, it was new to me, got it used off the board), and my P0138's went away.

FWIW, when I took the old one off, there was some moisture in the anti foul extender, enough to lightly coat my finger, and some slight corrosion on the body of the sensor. The new one warmed up nicely under power, suggesting that the heater part really had gone out on the old one.