Code 51 - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > TJ Jeep Wrangler Forum > TJ Tech Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 04-12-2007, 04:22 PM   #1
Newb
 
Join Date: Apr 2007
Posts: 12
Code 51

Hi, All

Would anyone know what a code 51 means?

51 A lean air/fuel mixture has been indicated by an abnormally rich correction factor.

Thanks

hecace is offline   Quote Quick Reply
Old 04-12-2007, 05:07 PM   #2
Jeeper
 
JCS05Rubi's Avatar
 
Join Date: Mar 2007
Location: central md
Posts: 2,748
I just wrote an entire paragraph and then deleted it before I posted it. I know, I am a moron..

Instead of re-typing everything I am just going to say this. Without knowing anything else about the truck (year, engine and trans, mileage, recent work, other driveability issues etc.) let alone being next to it, it is very hard to diagnose an issue. Especially without knowing any other codes besides this one.

With that said, I think your problem is PROBABLY going to be in your 02 sensors. A rich condition is usually only caused by 02 sensors or fuel injectors.

Now, do not go out and spent 300 bucks on 02 sensors just because i said so Check your air filiter, make sure its good to go and not dirty. ALSO CHECK YOUR INTAKE TUBBING AND THROTTLE BODY. Make sure nothing is in there blocking things up.

Next, go get your truck scanned. Have it hooked up to a scan tool, and see if and which 02 sensors are giving false readings.

Let us know what you find and we can help you better. Also, double check there are no other codes. A rich/lean code by itself with nothing else is pretty rare. Again, have your truck scanned for current and STORED codes, and also the 02 sensor readings at idle, cruise, and WOT and get back to us.


-Jason

__________________
Dad's Blog! http://justkeepliving.blog.com/
T-Shirts for Dad, based on his "Just Keep Living" philosophy. http://www.cafepress.com/justkeepliving


1997 Wrangler Sport - 5 spd. Retired
2005 Wrangler Rubicon - 6spd|KC 55watt fogs, IPF H4s with fatboys,Uniden CB radio/Teraflex mount
http://www.4x4s-pod.com/
JCS05Rubi is offline   Quote Quick Reply
Old 04-12-2007, 05:51 PM   #3
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 31,870
Images: 2
Replace your upstream 02 sensor, the one nearest the exhaust header.
__________________
Remember that having a different opinion doesn't also require one to be a jerk when expressing it.

When you have a choice, buy American.

Jerry Bransford is online now   Quote Quick Reply
Old 04-13-2007, 09:01 AM   #4
Newb
 
Join Date: Apr 2007
Posts: 12
Thanks for the replies.

It's a '97 TJ 4 cyl. 2.5L. It is throwing 2 codes: 12 and 51. The 12 probably comes from some diags work done at a local shop. They ran diags, but found nothing other than an oil pump sensor that in the end did nto fix anything. We are also having an issue witht he oil gauge dropping to 0 when idle. I am guessing that the oil pump needs to be replaced.

But this other mixture issue only happens when the car is run in 5th for a while on he highway. Does not happen around town.
hecace is offline   Quote Quick Reply
Old 04-13-2007, 09:27 AM   #5
Jeeper
 
JCS05Rubi's Avatar
 
Join Date: Mar 2007
Location: central md
Posts: 2,748
For the oil pressure issue, try and do an oil chane, using some thinner oil than normal, maybe some 0w30 is the lightest i would go. 5W30 will be fine if you still have 10w30 in it. Although if you issue is interrmitant, using ANY 30 wieght will produce the same result when warm.

Change your oil filter, they can and do fail. Do not use fram or k&n.

Any other issues are going to be reltivly major if the new sensor is good. Pump/blocked passages/maybe even a worn pump gear if ours arent electric.

Maybe a ground issue at the guage? just a guess.

Code P0012 is a retarded timing code if i remember right. Cant help ya there, gotta be near it for that.

Timing CAN set a rich/lean code if you are getting rich/lean misfires but its unlikley. My best advice at this point is to have it looked at in person. You could check the timing, and check the 02 sensor, but I dont know enough without being nect to the truck to give you solid advice.
__________________
Dad's Blog! http://justkeepliving.blog.com/
T-Shirts for Dad, based on his "Just Keep Living" philosophy. http://www.cafepress.com/justkeepliving


1997 Wrangler Sport - 5 spd. Retired
2005 Wrangler Rubicon - 6spd|KC 55watt fogs, IPF H4s with fatboys,Uniden CB radio/Teraflex mount
http://www.4x4s-pod.com/
JCS05Rubi is offline   Quote Quick Reply
Old 04-13-2007, 12:50 PM   #6
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 31,870
Images: 2
Code 12 is nothing more than that the battery has been disconnected in recent history. It'll eventually clear itself. A Code 12 has nothing to do with a P0012 like is used in newer TJs. Again, that 51 code is indicating your upstream 02 sensor is going/has gone bad.
__________________
Remember that having a different opinion doesn't also require one to be a jerk when expressing it.

When you have a choice, buy American.

Jerry Bransford is online now   Quote Quick Reply
Old 04-13-2007, 02:04 PM   #7
Jeeper
 
erickpl's Avatar
 
Join Date: Jan 2007
Location: Alabama
Posts: 2,305
Send a message via AIM to erickpl
Sorry for a small hijack....

Out of curiousity, what grade oil do the 4.0's use? I seem to recall my 2.5L manual stating something about using 10W30, but I'd have to double check that.

I've been using Mobil 1 10W30 for the last 3 years in my 2.5L and it has been running flawlessly and better than when I got it at 83k.
erickpl is offline   Quote Quick Reply
Old 04-13-2007, 02:23 PM   #8
Jeeper
 
JCS05Rubi's Avatar
 
Join Date: Mar 2007
Location: central md
Posts: 2,748
I THINK the 4.0s call for 10w30/5w30 depending on season, but I have not changed the oil in a 4.0 in 2 years, and mines not due for 2,000 more miles, so I am just guessing here..
__________________
Dad's Blog! http://justkeepliving.blog.com/
T-Shirts for Dad, based on his "Just Keep Living" philosophy. http://www.cafepress.com/justkeepliving


1997 Wrangler Sport - 5 spd. Retired
2005 Wrangler Rubicon - 6spd|KC 55watt fogs, IPF H4s with fatboys,Uniden CB radio/Teraflex mount
http://www.4x4s-pod.com/
JCS05Rubi is offline   Quote Quick Reply
Old 04-13-2007, 03:36 PM   #9
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 31,870
Images: 2
For some reason, Mobil-1 does not do well in the 4.0L engine. Aftermarket oil analyses have found Mobil-1 raises the iron content to an unusually high level. Personally I just run Valvoline but there are other equally good oils. 5W-30 in cold climates, 10W-30 in temperate climates.
__________________
Remember that having a different opinion doesn't also require one to be a jerk when expressing it.

When you have a choice, buy American.

Jerry Bransford is online now   Quote Quick Reply
Old 04-13-2007, 03:37 PM   #10
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 31,870
Images: 2
Quote:
Originally Posted by JCS05Rubi View Post
I THINK the 4.0s call for 10w30/5w30 depending on season, but I have not changed the oil in a 4.0 in 2 years, and mines not due for 2,000 more miles, so I am just guessing here..
Your engine's oil is due changing just due to the time it's been in the engine. Oil change intervals are not based solely on mileage.
__________________
Remember that having a different opinion doesn't also require one to be a jerk when expressing it.

When you have a choice, buy American.

Jerry Bransford is online now   Quote Quick Reply
Old 04-13-2007, 04:32 PM   #11
Newb
 
Join Date: Apr 2007
Posts: 12
Thanks, Jerry

I'll try replacing the upstream sensor and see what happens. Hopefully it'll do away with the "sputtering" in 5th gear.

Thanks again for everyone's feedback
hecace is offline   Quote Quick Reply
Old 04-13-2007, 06:03 PM   #12
Jeeper
 
JCS05Rubi's Avatar
 
Join Date: Mar 2007
Location: central md
Posts: 2,748
OH Jerry.. .Oh god no lol.. What I meant was that I sold my 97 4.0 2 years ago, and I just bought my 05 1,000 miles ago (dealer did oil change when I bought it). Not that I have driven my truck for 2 years without one

__________________
Dad's Blog! http://justkeepliving.blog.com/
T-Shirts for Dad, based on his "Just Keep Living" philosophy. http://www.cafepress.com/justkeepliving


1997 Wrangler Sport - 5 spd. Retired
2005 Wrangler Rubicon - 6spd|KC 55watt fogs, IPF H4s with fatboys,Uniden CB radio/Teraflex mount
http://www.4x4s-pod.com/
JCS05Rubi 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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Code Problem - P1294 davidsalazar03 TJ General Discussion Forum 4 03-06-2011 05:13 PM
Can't find paint code on sticker on a red YJ Graybeard YJ General Discussion Forum 3 01-10-2009 06:24 PM
Odd LJ paint code question rallykid TJ General Discussion Forum 3 01-06-2009 10:51 AM
code question Geepto TJ Tech Forum 8 07-26-2007 04:38 PM
Need the P-code for dash code 65 Buffalo97 TJ Tech Forum 9 06-15-2007 01:10 PM



» Featured Product

All times are GMT -5. The time now is 02:25 PM.



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