i was drivin around last night my car was fine....i get on the highway and doin like 75-80 and all the sudden my check engine light comes on.....so when i got home i put my code reader on it and the codes are

P0134
o2 Sensor CKT No Activity (Bank 1 Sensor 1)

P0138
o2 Sensor Circuit High Volts (Bank 1 Sensor 2)

can anybody please help me i don't understand it was fine and all the sudden check engine light is on

Okay the sensor no activity. The computer gets a signal voltage from every sensor on the car, it can come in analog or digital, but the computer will convert analog to digital before it goes in. Anyways either the sensor is complete dead and not reading any volts, actually O2 sensor switch rich to lean, rich to lean. but what gets me is the code isnt for slow switching, so the computer isnt even seeing anything, so that leads me to believe either two things. Your sensor is unplugged, or the sensor is bad.

Now your other sensor is saying high voltage.

Well basically the computer expects to the see the sensor within a certain per set range. If the sensor goes to far above or below the set range the computer will set a code.

You should bring this to a shop before just replacing two sensors. They have scan tools that can actually see what the sensors are doing.

Good luck



- 2004 Cavalier - 124k, owned since new

My guess is the 1st sensor took a dump, or came unplugged, or the wire was damaged somehow. That sensor isn't too bad to buy, but the 2nd one (after cat) is because it's a heated sensor. Because the 1st sensor isnt' working, the computer's tests of the 2nd sensor are giving bad readings (it compares the reading of the 2nd sensor to the 1st sensor), so that's likely the 2nd code.

Have a look to make sure the 1st sensor didn't get unplugged or damaged, then try replacing the 1st sensor, I'll bet that fixes it.


15.3 @ 89.97mph, 14's on the way?

i think its a pretty good possibility. I had the same problem a week ago i kept getting the 2 codes. So i went for the exhaust man. o2 sensor replaced it 2 days ago. I was driving last nite there goes the CEL again. But when i scanned it i was happy to see only th bank 1 sensor 2 code thus meaning my first one i installed must work u live in an area of alot of water? or have alot of miles.. i live in th desert but i had 170k miles.. its def. possible for them both to go out though

i just bought a new front sensor and just put it in......i think the back sensor is bad but yea i know a guy that owns a shop and he gives me discounts on hookin it up to his computer....so ill go to him even tho its really hard to scheadule a time to see him cuz hes so busy thats why i wanted to solve it myself