Check Engine Light - 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 06-02-2010, 04:24 AM   #1
Jeeper
 
Flameeater's Avatar
 
Join Date: Feb 2010
Posts: 20
Check Engine Light

I am getting codes 12, 21, and 51 on the odometer. Any ideas?

I am thinking of changing the O2 sensors, and the fuel filter, but... I went to the local parts store and want $125 for a fuel filter!! What gives!? That is insane! I have never seen a fuel filter cost more then 5-10 bucks. Was there a mistake? When he told me that I was like

Flameeater is offline   Quote Quick Reply
Old 06-02-2010, 05:20 AM   #2
Jeeper
 
rtread's Avatar
 
Join Date: Feb 2010
Location: Deep in the heart of Texas
Posts: 876
Where is the fuel filter on your Jeep? My fuel filter ('98 TJ) is in the fuel tank. My Haynes Repair Manual says "Only 1987 through 1995 models use a replaceble in-line fuel filter. The manufacturer does not suggest periodic fuel filter replacement on 1997 and later models. Since the fuel filter is part of the fuel pump assembly inside the fuel tank on 1997 and later models, refer to Chapter 4 if fuel contamination makes it necessary to replace fuel filter."

I have read the referenced Chapter 4 procedure and you gotta drop the fuel tank. My B-I-L did this on his Jeep to replace the fuel pump and he's still cussing it.

My guess is the $125 is for the pump/filter assembly.

__________________
Never argue with idiots......they will drag you down to their level then beat you with experience.
rtread is offline   Quote Quick Reply
Old 06-02-2010, 07:09 AM   #3
Jeeper
 
Brad[LK1]'s Avatar
 
Join Date: Jan 2009
Location: Western PA
Posts: 424
Send a message via AIM to Brad[LK1]
Fuel filter is in the tank....it's usually one of the ones that doesnt need replaced...unless you feel like dropping the tank. I think 12 & 51 are start test and end test hex codes...you can look up chrysler hex codes on the internet and proceed from there.
Brad[LK1] is offline   Quote Quick Reply
Old 06-02-2010, 10:13 AM   #4
Jeeper
 
burton160w's Avatar
 
Join Date: Oct 2009
Location: Underneath my TJ
Posts: 1,641
It's a whole pump assembly that sits inside your tank and isn't one of the in-line el-cheapo ones
  • 12 - Battery Disconnect Direct battery input to the PCM was disconnected within the last 50 key-on cycles
  • 21 - Left O2 Sensor Shorted to Voltage Left oxygen sensor input voltage maintained above the normal operating range
  • 21 - Upstream O2 Sensor Shorted to Ground; or Upstream O2 Sensor Heater Failure; or Upstream O2 Sensor Slow Response Upstream O2 sensor voltage too low, tested after cold start; or Upstream oxygen sensor heating element circuit malfunction; or Upstream oxygen sensor response slower than minimum required switching frequency
  • 21 - Downstream O2 Sensor Shorted to Ground; or Downstream O2 Sensor Heater Failure; or Downstream O2 Sensor Shorted to Voltage Downstream O2 sensor voltage too low, tested after cold start; or Downstream oxygen sensor heating element circuit malfunction; or Downstream oxygen sensor input voltage maintained above the normal operating range
  • 51 - Fuel System Lean A lean air/fuel mixture has been indicated by an abnormally rich correction factor

Rather then look at the fuel filter (which are usually pretty strong), look instead at replacing the O2 sensor, and then checking your MAP and TPS sensor. They're infamous for throwing a code 51. It may have simply gotten wet. Your map sensor and TPS sensor are located right next to the throttle body. Someone else may be able to post a picture that will help tremendously.



Also, what engine do you have? The 2.5L or 4.0L?
__________________
It's got a Willy's body, a Chevy engine, Ford axles, GM transmission, and Dodge steering components... it must be a Wrangler.
burton160w is offline   Quote Quick Reply
Old 06-18-2010, 05:12 PM   #5
Jeeper
 
Flameeater's Avatar
 
Join Date: Feb 2010
Posts: 20
Hey guys,
Sorry for the looooooonng delay in getting back to you. Had personal issues come up and haven't been online. Problem with Jeep is still present. As I haven't had time to tinker with it. My TJ is a 2.5 and it seems extremely sluggish and weak. On start-up it idles very rough. Also when getting off interstate it idles at about 2k for a good while before dropping down to 1k. It is guzzling gas like no body's business. A quarter tank in 30 miles of interstate driving. The check engine light is off as of now. It comes on then goes off.

How expensive is it to replace these sensors you spoke of? Is it difficult to clean the throttle body (saw that suggestion in another thread I think).
Flameeater 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
Check engine light gmccomas412 YJ Tech Forum 4 06-09-2010 10:08 PM
check engine light FrankTheTank TJ Tech Forum 3 03-11-2010 09:08 AM
Check Engine light - lean/rich JLS TJ Tech Forum 12 03-11-2010 12:09 AM
check engine light? NEED HELP shorty8914446 TJ Tech Forum 4 03-08-2010 04:26 PM
Check Engine Light vin211 TJ Tech Forum 4 04-07-2008 09:12 AM


logo carid shop wrangler parts carid fender flares custom wheels store avs deflectors at carid
» Rates
Get low rates on auto insurance in Canada!

» Network Links
»Jeep Parts
» Featured Product

All times are GMT -5. The time now is 03:09 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