Engine code

[The-Hurricane]

so my engine blew a code today, and i was like yay time to use the new scanner i got like 3 weeks ago!!

so the code that came up was: P0138 o2 sensor circuit, high voltage bank one, sensor 2.

is that like the o2 sensor on my intake? its kind of dumb on my part to only have the stuff to read it, and not to actually figure out what the code relates too. any help?

[Dukes69]

O2 sensors are in the exhaust. I'd start with the first on in line and move rearward from there.

[The-Hurricane]

is there one on the header? i know that there is one in the side of the cat. how can i tell if its bad or not? just replace it and hope for the best?

[dirtman13]

If you have the shop manual it should tell you what sensor that is.

[aw12345]

It means its the o2 sensor behind the last cat.
a 4cyl has only one bank of cylinders, sensor number 1 would be the first one (the one that controls fuel)
Number 2 measures catalitic converter efficiency. Could also mean that the converters failed, but its most likely the sensor

[The-Hurricane]

theres one after the cat? i know that there is one in the side of the cat..i dont need a cat here in canada. is there dummy plugs on the market for the sensor so i could just cut the cat and straight pipe it?

[Dukes69]

California Emissions equipped Jeeps have more o2 sensors then federal (or possibly export) Jeeps.

how many 02 sensors can you see? There should be at least 1 in the header and possibly another one downstream a ways (pre cat?)

[Giffer]

thats what i love about cali. ol terminator him self "runs" the shows and he is a big hummer guy. the state with the strongest emmission laws has the first civilian to own a hummer alpha. i dont think those things would pass emission laws without some bribery. here in canada we dont eeven need any od that crap. not that its a bad thing to have it, but still, we dont need it.
and in me yp its only one. nothing from the header back. straight pipe it. no need for back pressure.

[fun4wheelerguy]

The first o2 sensor tells the computer lean or rich so the computer can make adjustments.....

The second o2 sensor behind the catalytic converter senses changes of the fuel mixture between the front of the catalytic converter and the rear of the converter. If there are no changes the code will be set. Possibly a bad converter or oxygen sensors.
My experience is the catalytic converter gets lazy because of low grade fuels. My customers using Arco and USA gas is very common when asked. What kind of fuel are you using?

Using name brand fuel like Shell, 76 and Chevron has been proven to have better fuel mileage. Top tier fuels have addatives in them which clean injectors and the fuel system which keeps the engine clean and higher performance. I have seen that name brand fuel costs a little more but you will spend alot less at the repair shop later.

Brett

[aw12345]

Since it sets a code for the second oxygen sensor it stands to reson it ought to have 2 of them puppies. Like its said before all the second one does is measure catalytic converter efficency. When you straight pipe it, it should still run fine even though there is a good change it will loose some milage and power, the ecm is programmed to run with a cat and the amount of backpressure it creates. So it's a toss up if it will run better or worse, these days manufacturers do apretty good job of programming ecm's for good milage and power with all the emmision crap on there, tampering with it doesn't necesarilly improve things

[The-Hurricane]

im just wondering if cuting the cat, and un plugging the 02 sensor will just constantly bring up my check engine light

[aw12345]

Yes it will

[The-Hurricane]

is there any way to trick it? like i said earlyer, some sort of plug in thing? cross some wires?

[aw12345]

Easiest fix is to fix it properly. To trick it you would have to copy the signal it expects to see which is as I understand almost a flat voltage signal
Don't quite remember if its near 0.1 or 0.8 volts would think its near 0.1 volts