Something to remember about PCM failures

[Paul Ruggles]

I have noticed a few ' Is my PCM bad' threads lately.
A few observations I have made over the years of dealing with Chrysler PCMs and their wiring-

- PCMs fail rarely ..but they can.

- look into sensors first. If possible swap with a known good sensor. New bad ones happen and can send you down the wrong path.

- get the wiring diagram for your year jeep. This is important. You cannot properly diagnose shit without the wiring diagram.

- buy a ohm meter. Cheap ones usually are ok.

- check the wiring. Chrysler sucks at routing their wiring. Look for rub marks on the looms. If the loom has been rubbing on something for a while, the wiring inside could be damage. Use a meter to check from pin to pin on the connectors. ITS ALL IN THE FSM WIRING DIAGRAMS!

-When all else fails, start looking into PCMs. It could be bad, but assume something else is first.

Good luck. Wiring can be a pain in the ass, but if you want to play with 20 year old vehicles and not pay someone every time there is a problem, you need to how to deal with it.

 

[MallCrawlOnTons]

Please don’t include 05/06 in the catagory of “rarely fail”.

 

[Paul Ruggles]

Please don’t include 05/06 in the catagory of “rarely fail”.

I guess they may fail more often than the early ones, but does anyone know the actual percentage of failures? 1 percent or 20 percent? I would call 1 percent rare. I would call 20 percent common .

If I owned a 05/06 I would still troubleshoot the hell out of it before I looked for a new PCM.

Not trying to start an arguement. Just trying to pass on some troubleshooting ideas for new members.

 

[Wheeling diver]

Please don’t include 05/06 in the catagory of “rarely fail”.

Amazing how the 05 06 models seem to have all the fun stuff (pcm, opda) but still be my favorite years. Sometimes I think my mama dropped me on my head too much as a baby.

 

[MallCrawlOnTons]

I guess they may fail more often than the early ones, but does anyone know the actual percentage of failures? 1 percent or 20 percent? I would call 1 percent rare. I would call 20 percent common .

If I owned a 05/06 I would still troubleshoot the hell out of it before I looked for a new PCM.

Not trying to start an arguement. Just trying to pass on some troubleshooting ideas for new members.

Percentages would be guessing. We will never nail down a number. Buts it’s definitely not “rare” on a 2005 or 2006 model. More auto than manual.

 

[Chris]

Great advice and good info

 

[L J]

Percentages would be guessing. We will never nail down a number. Buts it’s definitely not “rare” on a 2005 or 2006 model. More auto than manual.

If one can't "nail down a number" how does one know it's "definitely not “rare”"?

 

[MallCrawlOnTons]

If one can't "nail down a number" how does one know it's "definitely not “rare”"?

A number is specific. Virtually impossible to find out specifically how many 05/06 Jeep owners have had a pcm issue and replaced it with a good known pcm and it fix the issue.
It’s a known common issue among the community, but again a number or percentage isn’t attainable in my opinion.

 

[BuildBreakRepeat]

The PCM failure in later TJs is so common that an entire company set out to fix it. @Wranglerfix

 

[Wranglerfix]

A number is specific. Virtually impossible to find out specifically how many 05/06 Jeep owners have had a pcm issue and replaced it with a good known pcm and it fix the issue.
It’s a known common issue among the community, but again a number or percentage isn’t attainable in my opinion.

It is impossible to say what percentage of the pcms actually fail. However, when the start failing, those pcms are not repairable...The automatics outnumber manuals about 30-1 as far as replacements.

Here is a video that shows how to test for circuit integrity for the 05-06’s.



Wiring is a pain to check but it needs to be done.

If you determine it is the pcm, please be careful of online sellers selling “known good” units. You can reset certain symptoms by disconnecting the battery but they will come back again leaving you where you started minus some money.

You can call me if you would like to discuss further.

 

[Chris]

The automatics outnumber manuals about 30-1 as far as replacements.

Can’t you disable the automatic functionality of the PCM so that it can be used in a manual equipped vehicle?

 

[Paul Ruggles]

I guess my point was a sensor or a wiring problem is more common, in my opinion, than a pcm failure. If people want to drop money on a new pcm everytime they get a check engine light, go ahead.

There is a process to troubleshooting .

Do the free or cheap stuff first.

Get familiar with the wiring diagrams and how the sensors give info to the pcm, and what the pcm does with the info.

Do not take anything for granted. Trust, but verify.

Do not take everything you read on the internet as gospel. There are alot of people who heard that someone may have had a failure of some sort, maybe, then posted on10 different sites.

If a person can not do the work themselves, then find someone you trust, and let them do it. This is tough for me. My belief is , if someone else can do a job, I can too if I have all the needed info.

If this comes off as a rant, I apologize. Been drinking for a while today .

 

[Wranglerfix]

Can’t you disable the automatic functionality of the PCM so that it can be used in a manual equipped vehicle?

I just sent the question to my tech as I am not certain. I will get the correct answer and reply.

 

[Chris]

I just sent the question to my tech as I am not certain. I will get the correct answer and reply.

Thanks! I know when I accessed the PCM on my 05 via HPTuners it had an option to enable or disable the automatic transmission functionality. However, I’m not sure if those settings did anything or not, as I didn’t actually have the balls to toy with it and potentially mess something up.

 

[Wranglerfix]

Thanks! I know when I accessed the PCM on my 05 via HPTuners it had an option to enable or disable the automatic transmission functionality. However, I’m not sure if those settings did anything or not, as I didn’t actually have the balls to toy with it and potentially mess something up.

Understood and very wise decision, sir!

I will post an answer later.

 

[Chris]

Understood and very wise decision, sir!

I will post an answer later.

Thanks, I look forward to it!

 

[Chris]

I guess my point was a sensor or a wiring problem is more common, in my opinion, than a pcm failure. If people want to drop money on a new pcm everytime they get a check engine light, go ahead.

There is a process to troubleshooting .

Do the free or cheap stuff first.

Get familiar with the wiring diagrams and how the sensors give info to the pcm, and what the pcm does with the info.

Do not take anything for granted. Trust, but verify.

Do not take everything you read on the internet as gospel. There are alot of people who heard that someone may have had a failure of some sort, maybe, then posted on10 different sites.

If a person can not do the work themselves, then find someone you trust, and let them do it. This is tough for me. My belief is , if someone else can do a job, I can too if I have all the needed info.

If this comes off as a rant, I apologize. Been drinking for a while today .

Well said, I agree 100%.

 

[Jeeper_Creeper]

I think this thread brings up the extremely important point of proper troubleshooting.

I once had a Toyota pickup with a 22RE and about a year after having the engine rebuilt, it had a huge hiccup on the interstate and wouldn’t run properly. It was like it was only running on 3 cylinders (it was). Troubleshooting codes were throwing all kinds of crazy ideas and every junkyard part I threw under the hood didn’t seem to help. It took nearly 6 months for me to finally start taking things apart to find that the engine rebuilder routed the injector harness wrong which cause a tight spot that took a year to rub through and ground out some wires. I quick couple of wire splices and that thing was good to go. I was so sick of that truck at that point that I quickly sold it and never looked back.
If only we had helpful forums back then...

 

[Chris]

I just sent the question to my tech as I am not certain. I will get the correct answer and reply.

Did you ever hear back about this Mark?

 

[mrblaine]

The PCM failure in later TJs is so common that an entire company set out to fix it. @Wranglerfix

Nothing against WF since we use them with perfect success but there were many companies addressing the issue long before Mark started WF. Had you said they approached the issue with a different mindset, that I would wholly agree with.