So I pulled my codes and I got a P0138, the book says "02 sensor circuit high voltage (bank 1 sensor 2)".

I cleared the code and will have to drive to see if it comes back.

Any thoughts on the cause?

 

bad o2 sensor , i had the same problem , replace the one on the down pipe

 

ok so it is the one before the cat?

 

That's the downstream O2 sensor, it should be just after the catalytic converter.

Go find it and make sure that it looks OK and that the wires are OK.

Mine threw this code and another ( I forget what ) when I managed to break the O2 sensor.

 

yes , i cant rememer my code it thru off hand but im pretty sure it was that same exact one and mine was the one before the cat , you grab a bosch sensor from auto zone for about 60 bucks i beleive

 

thats the down stream one ? i couldve sworn mine was that same code , but i know mine was up stream , my bad

 

Indeed it is the one after the cat, thanks guys!

http://www.obd-codes.com/p0138

 

20 miles or so later the code came back. I guess I need to order a new sensor.

Any tips on changing it? Open end (size?) wrench best?

 

Go buy some PB Blaster.

An open ended wrench is the only option, and that sucker is not gunna want to come off, hence the PB Blaster...

 

7/8" closed end of the wrench, unplug the sensor and work the wire through til it's not in the way. If you use the open end, your gonna slip and rake your knuckles or round the bolt. Best bet to break it loose is to warm the car up first (expands the exhaust) and expect to use some severe force to break it loose. Not sure where the PB recommendation is coming from since your not gonna be able to get any of the threads with it and it's there fore useless on this part (excellent when you can hit the threads). I get the wrench on there good and push with my foot to break them loose. They also make a specific socket for 02 sensors, but that's a waste of money.

 

had the same exact problem (p0138) code pop up. replaced both o2 sensors, they were ready to be replaced anyways. code came back (p0138) high voltage. come to find out it was a missed fuse in the fuse block next to the batery in the engine compartment. changed the fuse, cleared the code. have drove over a 1000 miles and no problems.

 

Before you do anything!! Check the fuse(15 amp) under the hood, it blows and comes up with this code. Went through hell with this!!