2000 xj check engine light question

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Jan 4, 2011 | 02:55 PM

#16

black2000xj

Thread Starter

Seasoned Member

Joined: Jan 2011

Posts: 493

Likes: 0

From: Grand Haven, Michigan

Year: 1999

Model: Cherokee

Engine: 4.0 I6

code

i feel sorry for you, but mine was a pain, prolly the originals, rusted in there like crazy, a little wd40, light tapping with a hammer and a good breaker bar
seemed to take care of it

the code was still being thrown after the sensors were in, but after doing the computer reset thing, code is gone, jeep idles smoother, seems to run alot more efficient, i think anyway

hoping my mileage will go up too (fingers crossed)

although 275 miles to a tank isnt bad, i wouldnt mind getting closer to 300!

if your going to replace them, make sure you clean your throttle body really good before you do (with the old sensor in), then run it for a while.
then put the new sensors in, put a new air filter in to while your at it, it all helps JUST FYI
goodluck

Apr 16, 2011 | 07:34 AM

#17

Coolwnc

Newbie

Joined: Jan 2011

Posts: 3

Likes: 0

From: Asheville, North Carolina

Year: 2001

Model: Cherokee

Engine: 4.0 liter

Check engine light

I have a 2001 xj that has a check engine light on! It only comes on when I tow my utility trailer! I take it and have the code checked and it says miss fire on #3, so I put is new plugs. I drive it 1000 miles no light on. I hook up my trailer and go to Lowes to pick up mulch. Empty no check engine light, load trailer head home light comes on and stays on! It must be the weight of the trailer! Can anyone help me or any ideas on how to resolve this! Thanks

Apr 16, 2011 | 11:40 AM

#18

tjwalker

CF Veteran

Joined: Nov 2010

Posts: 5,841

Likes: 117

From: In the middle of Minnesota!

Year: 1999

Model: Cherokee

Engine: 4.0

Quote:

Originally Posted by Coolwnc

Could be a couple of things. Two come to mind.

1. 00-01 is more susceptible to "heat soak", where you may get the check engine light when engine bay is hot, especially after restarting a hot engine. SEARCH and you will find a lot of information about heat soak

2. Some people have been having mysterious misfires with Bosch spark plugs. Not all to be fair, but enough to warrant remembering this. If you are running Bosch plugs, I would swap them out to NGK.

Apr 16, 2011 | 11:59 AM

#19

crystalion

Seasoned Member

Joined: Dec 2010

Posts: 275

Likes: 0

From: NY

Year: 2000

Model: Cherokee

Engine: 4.0

Quote:

Originally Posted by tjwalker

You could try the below procedure. If it still does it after this, the problem still exists and you need to continue to look for the root cause.

---------------------------------------

This procedure is for OBDII Jeeps.

This six step procedure will erase the “Adaptive Memory” stored inside the PCM and allow a new “Adaptive Memory” to be developed. After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics.

Perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn Mode adaptive mode.

1. Disconnect the POSITIVE battery Terminal and touch it to ground for 30 seconds. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.
2. Reconnect the Battery Cable
3. Turn Ignition Switch to the “On” position but DO NOT start the engine
4. Turn Headlight “On”
5. Turn Headlights “Off”
6. Turn Ignition Key “Off”

The PCM Adaptive memory has now been flashed, or erased from the PCM.
When you start the engine it will be running off a set of pre-programmed values that come with the PCM from the factory. When you get the engine up to operating temperature the PCM will start to collect data for the “Adaptive Memory”. The PCM will collect data for Adaptive Memory for the first 50 warm-up Cycles.

I have done this with many cars. After fixing whatever the defective part was and clearing the code the CEL would come back on. So assuming it has memory and since I worked on PLCs on machinery ( we would have to sometimes cut the main power to clear or readjust the machine-many capacitors holding charges keeping its brains alive). After basically taking the positive lead off and walking away - reattaching -the code was no more.