Engine Light codes? - JeepForum.com
 
LinkBack Thread Tools
post #1 of 9 Old 12-17-2013, 06:30 PM Thread Starter
Zyurazek
Registered User
1995 YJ Wrangler 
 
Join Date: Dec 2013
Location: Spotsylvania
Posts: 135
Engine Light codes?

Hello, I am new to this forums. I signed up after reading many topics on here for help with my Wrangler. I am new to the world of Jeeps. I purchased my 95 Wrangler SE 4.0L standard shift a few weeks ago. I had my engine light come on. After getting the codes, I was left a little stumped. The codes came in this order: 12 (battery disconnect), 51 (rich mixture I believe), 21,21 (that is no error, 21 registered twice. I am stumped as to why is flashed twice.), then a 55 which is the end of the codes. Is the 51 and 21 due to an O2 sensor? Does anyone have any idea why 21 would flash twice? I would appreciate any thought! I've searched the topic and there was only 1 other post a couple years ago, but there was no solution.

Thank you!

Zyurazek is offline  
Sponsored Links
Advertisement
 
post #2 of 9 Old 12-17-2013, 06:59 PM
Louie4
Rickety Wrecked Son!
 
Louie4's Avatar
1993 YJ Wrangler 
 
Join Date: Aug 2008
Location: Raleigh
Posts: 10,567
Sounds like an O2 sensor based on what you've said. You may always want to check the catalytic converter also. If they start to clog they will heat up the sensor and burn it out.

Lou

I have a jeep...and it is modified...I win.

YJOTM July 2012
YJOTM February 2014

Louie4's YJ Build
Poison Spyder Fender Install
Warn M8000 Rebuild Adventure
University of Georgia
Louie4 is online now  
post #3 of 9 Old 12-17-2013, 07:05 PM Thread Starter
Zyurazek
Registered User
1995 YJ Wrangler 
 
Join Date: Dec 2013
Location: Spotsylvania
Posts: 135
The exhaust from the header to the muffler has all been replaced just 3 weeks ago.
Zyurazek is offline  
post #4 of 9 Old 12-18-2013, 04:46 AM
Mark05059
Registered User
1989 YJ Wrangler 
 
Join Date: Mar 2009
Location: quechee Vermont
Posts: 4,697
check for a leak near the head or header.

1998 ZJ 5.2 Auto

1989 Wrangler Black Bone Stock 2.5l 5spd
/l , [____],
|---L--[]lllllll[]-
()_) ()_)==O=)_)
Mark05059 is offline  
post #5 of 9 Old 12-18-2013, 05:51 AM
pete1991YJ
Registered User
1991 YJ Wrangler 
 
Join Date: Mar 2012
Location: Niagara Falls
Posts: 1,876
Welcome to JeepForum, you've just found one of the best jeep sites anywhere!

The other guys are right, it sounds like an O2 sensor problem or possible a header leak. They are known to get loose near the back of the engine, I usually snug up the manifold bolts a couple times a year just to be sure. It only takes a few minutes with a 9/16 wrench.

After you get done you can reset the computer by disconnnecting the battery for a minute. The drive it for a bit and see if the error comes back. If it does then I would consider the O2 sensor.

hope that helps!

***--- Wrecking Crew member ---***
"I've prolly been around longer than you think"
pete1991YJ is offline  
post #6 of 9 Old 12-20-2013, 06:25 PM
laybackman
Bikini Bridge Inspector
 
laybackman's Avatar
2010 JK Wrangler 
 
Join Date: Dec 2002
Location: Massachusetts
Posts: 6,882
code 21 21 is code 33 AC issues if you have no AC that is the issue

Any leak in the intake system from a loose throttle body to a crack in the exhaust to a loose O2 sensor will cause a false lean code and make the engine run quite rich.

The O2 sensor detected oxygen in the exhaust stream and sets the DTC.

The O2 sensor is usually the least guilty for the O2 sensor code. A leak allowing atmospheric air into the system is the usual culprit.

Do you know what was good about the good old days? I wasn't good, And I wasn't old!

Senators and Congressman should wear uniforms like NASCAR drivers so we could identify their corporate sponsors....
laybackman is offline  
post #7 of 9 Old 12-22-2013, 07:14 PM Thread Starter
Zyurazek
Registered User
1995 YJ Wrangler 
 
Join Date: Dec 2013
Location: Spotsylvania
Posts: 135
Thanks for all the help! I've checked some things over and I've come up with having a bad sensor. I'll be replacing that sometime tomorrow to see if that's the definite fix!

For the 21-21 code being for the AC, I do have AC in my Jeep, and it seems just fine. I cracked it up today since the weather decided to go anti-winter and climb up to 70 plus degrees. What could it be if physically it feels fine?
Zyurazek is offline  
post #8 of 9 Old 12-22-2013, 07:48 PM
laybackman
Bikini Bridge Inspector
 
laybackman's Avatar
2010 JK Wrangler 
 
Join Date: Dec 2002
Location: Massachusetts
Posts: 6,882
Quote:
Originally Posted by Zyurazek View Post
Thanks for all the help! I've checked some things over and I've come up with having a bad sensor. I'll be replacing that sometime tomorrow to see if that's the definite fix!

For the 21-21 code being for the AC, I do have AC in my Jeep, and it seems just fine. I cracked it up today since the weather decided to go anti-winter and climb up to 70 plus degrees. What could it be if physically it feels fine?
I WAS WRONG!

DTC 21 = O2 sensor stays at center or shorted to voltage. Neither rich or lean condition detected from the oxygen sensor input.

If the wiring is good then the sensor is probably junk

Do you know what was good about the good old days? I wasn't good, And I wasn't old!

Senators and Congressman should wear uniforms like NASCAR drivers so we could identify their corporate sponsors....
laybackman is offline  
post #9 of 9 Old 12-22-2013, 07:55 PM Thread Starter
Zyurazek
Registered User
1995 YJ Wrangler 
 
Join Date: Dec 2013
Location: Spotsylvania
Posts: 135
Quote:
Originally Posted by laybackman
I WAS WRONG! DTC 21 = O2 sensor stays at center or shorted to voltage. Neither rich or lean condition detected from the oxygen sensor input. If the wiring is good then the sensor is probably junk
Makes more sense! Thank you!
Zyurazek is offline  
Reply

Tags
check engine light

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

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.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



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 On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome