Can't check codes?

**czjeeper** · 12-06-2007, 10:31 PM

I just threw a set of plugs, cap, rotor, fuel filter, fluids in my 2.5 YJ yesterday.
It was running better than ever.
I had it detailed today to include an under hood cleanup, and now my check engine light comes on.
Problem is, I can't seem to pull the code.
I tried the on/off, on/off, on...but nothing.
What am I dong wrong?
I'm assuming that the steam clean got moisture somewhere, but the thing runs great!
Help!

**70sElvis** · 12-07-2007, 07:28 AM

Does the CE light just stay on all of the time or does it come and go? It may hve had moisture in something that has since dried out. Not sure on Jeeps but on other vehicles, you have to go so many miles before it will reset itself or sometimes you can do something to reset it manually. Maybe like pulling the negative cable off for about 15 minutes.
Some Jeep PRO needs to either agree with me or shoot me down but hopefully this will help you.

**rustywrangler** · 12-07-2007, 07:48 AM

As said above, does the check engine light stay on?? You should be able to pull the codes. Did you do it in under 5 seconds???

**rustywrangler** · 12-07-2007, 07:49 AM

Quote:

Originally Posted by 70sElvis

Does the CE light just stay on all of the time or does it come and go? It may hve had moisture in something that has since dried out. Not sure on Jeeps but on other vehicles, you have to go so many miles before it will reset itself or sometimes you can do something to reset it manually. Maybe like pulling the negative cable off for about 15 minutes.
Some Jeep PRO needs to either agree with me or shoot me down but hopefully this will help you.

Either wait for 50 cycles of starting/turn off or just unplug the batt for more than 30 seconds and that will clear the code.

**czjeeper** · 12-07-2007, 11:04 AM

I definately do the key thing in under 5 seconds.
I'll pull the battery and see if that helps.
Thanks!

**czjeeper** · 12-08-2007, 01:31 AM

This morning I took it to my local parts shop, and they pulled 21 for a code...bad O2 sensor.
I replaced it, old one looked pretty toast. New one is a Bosch.
So, everything is fine....then a few hours later, 21 again.
Am I killing o2 sensors, or is something else wrong here?
Help!

**rustywrangler** · 12-08-2007, 01:33 AM

Check to see if your cat converter is rattling or plugged up. That will fowel up an 02 sensor fast.

**jay-h** · 12-08-2007, 07:01 AM

Probably not killing O2 sensors, remember the code is triggered when the system feels it is not getting the right signal from the O2. Wiring and connections would be the first point to look.

Blanning · 12-08-2007, 02:35 PM

You said you had it detailed, to include under the hood clean. I'll put my money on moisture somewhere it shouldn't be. The detailer probably shot amor-all or water in the wrong place. Start unplugging any connector related to the O2 circuit, spray it with drier, follow up with electrical grease. It's gonna be a pain in the neck, but if you are systematic and patient, you'll eventually get the fix.

**czjeeper** · 12-17-2007, 12:58 AM

Okay, I checked everything I could disconnect, and dried it.
I am still pulling codes 21) O2S stays at center or O2S shorted to voltage, and 51) O2S signal stays below center (lean).
This is a brand new Bosch sensor. What are the chances that it is faulty?
I have all new oil in the motor, cleaned and re-oiled my intake filter, and seafoamed my fuel system.
Also found that my temp gauge sending unit was busted. Fixed now and the gauge works, but my water temp is around 160. PO might have installed a cold t-stat. I know cooler t-stats produce worse fuel economy, and heightened engine wear...can it screw with the 02 sensor?
I am going to swap back to the factory 195 unless you guys have something to say about that...

dgm5186 · 12-17-2007, 01:12 AM

Chances are your sensor is faulty. I say this because my O2 sensor went bad a few months back and my mechanic replaced it with a bosch. Was puzzled since after he cleared the codes the check engine light came back on and I was still getting godawful mileage. Brought it back to him and come to find out, the sensor was sticking and not operating properly. Replaced again and problem is solved.

**4x4grey88** · 12-17-2007, 01:21 AM

Go to AutoZone Parts and ask them to borrow the OBD reader. They will ask you for a DL and credit card for collateral. You should be able to get the codes and make the repairs.

If you want to just reset the computer without getting the codes you can un-plug the battery and turn the ignition key to start (three times) and reconnect the battery. the CE light will be off, although it probably will come back on later on in time (after the computer recycles).

Try the first suggestion first.

Burnerman · 12-17-2007, 09:26 AM

Put the right Tstat in. With a 160* tstat your engine is not getting hot enough to go to closed loop running. It's running to rich and possibly fouling the O2 sensor. Check the cat like Rusty said, If it's been running cold/ rich there's a good chance it's clogged or close to it. After those things are good slap in a new O2 sensor.

**czjeeper** · 12-17-2007, 10:41 PM

The cat is brand new.
Today I installed a 195 t-stat. The old one was actually a 180. It's strange that it only heated to 160..?
I warranty exchanged the O2 sensor today, and so far so good!
It's running better than ever!
I also have a set of injector o-rings that I will install. Every now and then I get a whiff of gas, and figure it can't hurt put new ones in!

**czjeeper** · 12-19-2007, 06:06 PM

Okay, as you can tell, I modified the name of this thread.
As you may have gathered, I am going nuts with this O2 sensor business!
Today, the CEL cam on again...code 21...O2 sensor!
Soooo, how the heck is the motor killing these things? I have checked all the harness, and there are no shorts.
Again, this is a Bosch heated replacement, not a universal.
Motor temp is correct with the factory t-stat.
I am at my witts end! Help!

12-07-2007, 07:48 AM	#3
rustywrangler Got my eye on you..... Join Date: Apr 2005 Location: Syracuse, NY Posts: 18,657 Profile Gallery Classifieds My Jeeps	As said above, does the check engine light stay on?? You should be able to pull the codes. Did you do it in under 5 seconds??? __________________ http://i131.photobucket.com/albums/p...k_banner-1.gif Congenital Heart Disease is a reality for me, BOTH of my children have it. Please read up and become aware for future generations Lydia Ann-Acquired 08/05/05 Open Heart surgery 08/10/05 Jacob Patrick-Acquired 01/17/08 Open Heart surgery 02/15/08

12-08-2007, 01:33 AM	#7
rustywrangler Got my eye on you..... Join Date: Apr 2005 Location: Syracuse, NY Posts: 18,657 Profile Gallery Classifieds My Jeeps	Check to see if your cat converter is rattling or plugged up. That will fowel up an 02 sensor fast. __________________ http://i131.photobucket.com/albums/p...k_banner-1.gif Congenital Heart Disease is a reality for me, BOTH of my children have it. Please read up and become aware for future generations Lydia Ann-Acquired 08/05/05 Open Heart surgery 08/10/05 Jacob Patrick-Acquired 01/17/08 Open Heart surgery 02/15/08

12-08-2007, 02:35 PM	#9
Blanning Registered User Join Date: Dec 2007 Location: West Point Posts: 8 Profile Gallery Classifieds My Jeeps	You said you had it detailed, to include under the hood clean. I'll put my money on moisture somewhere it shouldn't be. The detailer probably shot amor-all or water in the wrong place. Start unplugging any connector related to the O2 circuit, spray it with drier, follow up with electrical grease. It's gonna be a pain in the neck, but if you are systematic and patient, you'll eventually get the fix.