Check Engine Light

[Joe Blogs]

My check engine light came on a few days ago. I turned the key 3 times and the code came up for O2 sensors (as expected). The light's been on for a few days now. I have the 4 new sensors all ready to be installed and I have the required tools to do the job. Thanks to my reading of this forum, I knew what to do in this instance. I sprayed some penetrating oil on the 4 sensors yesterday and again today so that they should be a little easier to get out when I get around to removing them.

After spraying them this afternoon, I get in the Jeep, start it up and the check engine light is no longer illuminated.

Does this mean anything? Do I still need to change the sensors? Do I just drive on until the light comes on again?

 

[Tob]

It will probably be back when the computer detects the conditions that triggered the diagnostic code again. I'd go ahead and replace them, especially since you already bought the parts.

 

[TJ Jim]

Mine came on once a long time ago. (8months or more) Reset it it and it’s never come back on. Watching the o2 voltage one reads a bit higher than the other so I’m guessing it has an off brand sensor reading too rich.

 

[SSTJ]

My check engine light came on a few days ago. I turned the key 3 times and the code came up for O2 sensors (as expected). The light's been on for a few days now. I have the 4 new sensors all ready to be installed and I have the required tools to do the job. Thanks to my reading of this forum, I knew what to do in this instance. I sprayed some penetrating oil on the 4 sensors yesterday and again today so that they should be a little easier to get out when I get around to removing them.

After spraying them this afternoon, I get in the Jeep, start it up and the check engine light is no longer illuminated.

Does this mean anything? Do I still need to change the sensors? Do I just drive on until the light comes on again?

Do you know how old they are, or when they were last replaced? If not then like @Tob said, I'd go ahead and replace them.

 

[Bighammer]

My check engine light came on a few days ago. I turned the key 3 times and the code came up for O2 sensors (as expected). The light's been on for a few days now. I have the 4 new sensors all ready to be installed and I have the required tools to do the job. Thanks to my reading of this forum, I knew what to do in this instance. I sprayed some penetrating oil on the 4 sensors yesterday and again today so that they should be a little easier to get out when I get around to removing them.

After spraying them this afternoon, I get in the Jeep, start it up and the check engine light is no longer illuminated.

Does this mean anything? Do I still need to change the sensors? Do I just drive on until the light comes on again?

Can you please explain the key-turning thing? I’ve never heard about it before

 

[SSTJ]

Can you please explain the key-turning thing? I’ve never heard about it before

Sure, I just learned that one too. It's described in Section 25 of the FSM (at least, it is in my 97 FSM). Or see here.

 

[Joe Blogs]

It came back on today as expected.

Did you get the explanation Big Hammer?