Why does it come and go? - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > JK Jeep Wrangler Forum > JK General Discussion Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 01-02-2013, 08:16 PM   #1
Newb
 
Join Date: Jan 2013
Posts: 4
Lightbulb Why does it come and go?

Hi, recently got an 09 rubicon 4 door auto trans w/ 77,000, the cel is on and calls for codes po138 & po158, however the light comes on for a few days then off, changed the sensors nothing. Dealer said it had a new cat. put in checked all the exhaust that seems gd. Going to work my way through the wires next. Any other ideas before I dig in, possibly a faulty PCM or expasion tank problem? Thanks for any ideas!

09rubakon is offline   Quote Quick Reply
Old 01-03-2013, 03:13 AM   #2
Jeeper
 
Rtone1583's Avatar
 
Join Date: Oct 2012
Location: Colorado
Posts: 414
A couple of things I found on another site:
  • Faulty O2 sensor
  • Short to battery voltage in O2 sensor signal circuit
  • High fuel pressure, possible high fuel pressure can over rich the system. (not as likely)
The first one is pretty much ruled out since you already replaced the sensors.

The second one, I'm kind of leary of in this instance since P0138 is 1st bank 2nd sensor and P0158 is 2nd bank 2nd sensor. I'm not 100% sure but I don't think that the sensors share a common path to the PCM, i.e. each reports independently to the PCM via its own path and it would seem unlikely, to me at least, that each path would short to battery intermitantly. One easy way to check would be to disconnect the harness from each sensor and check for power without the key on. If it is shorted to battery voltage, you should see ~12V at the connector.

The third one seems a little more likely to set intermitant codes in both sensors since an over rich condition would be seen by the entire system and could, in theory, be intermitant if the fuel system is surging for some reason.

As to why the light comes on for a few days and then goes off, the computer will clear some codes after a certain number of good run cycles so the code may be cleared one day only to be reset on the next.

Rtone1583 is offline   Quote Quick Reply
Old 01-03-2013, 04:13 PM   #3
Newb
 
Join Date: Jan 2013
Posts: 4
Thanks that helped to better understand the intermitancy problem. I thought once the cel came on it had to be cleared in order to go off. I will continue looking into the possible fuel issue. Thanks
09rubakon is offline   Quote Quick Reply
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Jeep Wrangler Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




» Network Links
»Jeep Parts
» Featured Product

All times are GMT -5. The time now is 09:13 AM.



Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC.
Wranglerforum.com is not in any way associated with the Chrysler Motors LLC