05-06 PCM issue is solved

Inherited-LJ said:
@Wranglerfix @thump365

Read all 24 pages.. thanks for everyone’s input and WranglerFix for a great solution.

Just want to make sure what’s going on with me is the same issue (I think so after reading all this).

I also have an 04 LJ, and twice now I have also gotten into a situation where it will not shift out of 1st gear. I just got this jeep (inherited it, hence the username) so I havent driven it much and don’t remember much “hard shifting”, but I also might have just been chalking that up to being a close to 20 year old Jeep and not thinking much of it. The “not shifting out of low gear” is obviously very noticeable though. CEL is on, but I don’t have a reader so don’t know the codes.

I saw the posts about unplugging the battery for 10 minutes, and if that solves the problem, it’s a 99% chance it’s the PCM. So I tired that, and there you have it… the CEL is gone and shifting fine now. That obviously leads me to believe the PCM is failing.

My question is this seems to be a problem with the 05-06 models, but I have an 04. I did see an early post on this tread from @Wranglerfix that this also affects some late model 04s. If I send you my VIN can you tell if it’s a late model 04 and likely has an issue with the PCM?

@thump365 - did you end up solving this problem? And if so, was the solution a PCM from @Wranglerfix ?
Click to expand...
To read the codes flip the ignition from the off position to on 3 times. They should print out in the odometer.
 
rasband said:
To read the codes flip the ignition from the off position to on 3 times. They should print out in the odometer.
Click to expand...
Thank you and good to know. I don’t have the CEL anymore now because I did the battery disconnect. Will it still show the codes even tho there is not CEL?
 
rasband said:
Keep driving it, you should get another code, that one by itself isn’t usually helpful :(
Click to expand...
Yea I’ve read that is basically just a “problem with the trans” code, but doesn’t tell you what the problem actually is… I read I need a code reader to see what other codes are there… is that true or if I keep driving, the other codes will show up with the 3 cycle trick?
 
Inherited-LJ said:
Yea I’ve read that is basically just a “problem with the trans” code, but doesn’t tell you what the problem actually is… I read I need a code reader to see what other codes are there… is that true or if I keep driving, the other codes will show up with the 3 cycle trick?
Click to expand...
If you own a Jeep, it's probably a good idea to go to Harbor Freight or get on Amazon and buy a code reader. You can get a decent one in the $50-70 range. 🙂
 
  • Like
Reactions: rasband
Inherited-LJ said:
Yea I’ve read that is basically just a “problem with the trans” code, but doesn’t tell you what the problem actually is… I read I need a code reader to see what other codes are there… is that true or if I keep driving, the other codes will show up with the 3 cycle trick?
Click to expand...
They should eventually, if you read the service manual here (search “FSM”) it will likely give you a few things to check based on that code and year.

edit, here’s the post:

https://wranglertjforum.com/threads...ice-manuals-fsm-technical-documentation.4618/
 
SoCalGlide said:
If you own a Jeep, it's probably a good idea to go to Harbor Freight or get on Amazon and buy a code reader. You can get a decent one in the $50-70 range. 🙂
Click to expand...
Lol yes probably should. My brother in law is a mechanic and has been helping me with this LJ, and he’s got all kinds of fancy tools. But probably not a bad idea to get a reader of my own anyway.
 
  • Like
Reactions: SoCalGlide
Update: did more investigating, and confirmed my LJ does NOT have the TCM as a part of the PCM. It is a separate unit.
That obviously does not solve anything… but if I do have to replace the whole unit, at least it’s not the whole PCM. At this point, I’ll take the small victory.
 
Inherited-LJ said:
Update: did more investigating, and confirmed my LJ does NOT have the TCM as a part of the PCM. It is a separate unit.
That obviously does not solve anything… but if I do have to replace the whole unit, at least it’s not the whole PCM. At this point, I’ll take the small victory.
Click to expand...
That’s an 05/06 issue, so that’s great!
 
SoCalGlide said:
If you own a Jeep, it's probably a good idea to go to Harbor Freight or get on Amazon and buy a code reader. You can get a decent one in the $50-70 range. 🙂
Click to expand...
You have any recommendations for a code reader I can order on Amazon that will pull the trans codes? I read somewhere that some readers won’t pull transmission codes and some do. I want to make sure the one I get can read the trans codes. But I also don’t want to spend $300 lol
 
Inherited-LJ said:
You have any recommendations for a code reader I can order on Amazon that will pull the trans codes? I read somewhere that some readers won’t pull transmission codes and some do. I want to make sure the one I get can read the trans codes. But I also don’t want to spend $300 lol
Click to expand...
I can't personally recommend this one, as I don't own it, but it claims to read transmission codes, seems to have good reviews, and is reasonably priced.
Code Reader
 
Just Installed mine and its working great. The TJ started right up, no cel and the shifting is extremely smooth now. Mark is a great guy to deal with, excellent costumer service.
 
  • Like
Reactions: skrelnik
Received my Wranglerfix PCM and installation was a snap. I have a 2005 manual that had a CEL with all four O2 sensors on, for the past 6-7 years.

The Wranglerfix PCM is working great, CEL is off, and the Jeep drives like it did back in the early days when I picked it up. It drove so smoothly after the fix.

Next up is passing emissions, so I need a couple hundred more miles and off to the test center.

I am knocking on wood as I type this, but thanks Mark, this is awesome!!!

IMG_20210812_143536.jpg
 
  • Like
  • Love
Reactions: DickD1911, Irun, Wranglerfix and 2 others
Unfortunately my CEL came back on today, but this time it is not giving me all four O2 sensors, and saying 0431.

@Wranglerfix - any thoughts?

@Jerry Bransford - in an older post you mentioned a cat could be the issue related to this code. Before spending a lot of money on new cars, is there anything else to check? My Indy has a fancy snap-on code reader, would that device disclose any material informational that my cheap code reader is not?
 
  • Like
Reactions: Wranglerfix
skrelnik said:
Unfortunately my CEL came back on today, but this time it is not giving me all four O2 sensors, and saying 0431.

@Wranglerfix - any thoughts?

@Jerry Bransford - in an older post you mentioned a cat could be the issue related to this code. Before spending a lot of money on new cars, is there anything else to check? My Indy has a fancy snap-on code reader, would that device disclose any material informational that my cheap code reader is not?
Click to expand...
I had a bad pre-cat that caused O2 sensor codes and a rough idle/misfires. I didn't know that until replacing the cats stopped all the problems. I had to replace the cats, one of the pre-cats came apart inside and blew its innards down into the main cat plugging it nearly completely. I don't know how to test for a bad precat though.
 
  • Like
Reactions: Wranglerfix and skrelnik
Jerry Bransford said:
I had a bad pre-cat that caused O2 sensor codes and a rough idle/misfires. I didn't know that until replacing the cats stopped all the problems. I had to replace the cats, one of the pre-cats came apart inside and blew its innards down into the main cat plugging it nearly completely. I don't know how to test for a bad precat though.
Click to expand...

What brand of precat did you go with?

My thought is to remove the Wranglerfix PCM and return to stock and then replace the precats and see the results. Does that get the Jerry stamp of approval or something else?
 
  • Like
Reactions: Wranglerfix and 5632
  • Like
Reactions: Wranglerfix
Top Bottom
Back