PCM Failure Potential on 05-06

UND_Sioux

UND_Sioux

TJ Enthusiast
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Oct 22, 2020
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Location
Montgomery, TX
I have a 2006 LJ 4.0/Auto and an extra good frame. My plan is to do my upgrades on the other frames, and then swap the body over.

i’ve done LS swap‘s before, but I kind of wanted to go a different direction this time and do a stroker. My concern is that I spend time and effort on the stroker and then I have a PCM problem in the future. The @Wranglerfix page says that their PCM is not tuneable which makes it unable to be used for a stroker build.

How common is the PCM failure on the 05-06? Are we talking one out of 10, one out of 100, one out of 1000?

Can the pre-05 computers and harnesses mate up to the Jeep?

Thanks.
 
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PCM failed in my 06 42rle equipped sport. Seems to be common on enthusiast forums but who knows the actual percentage of the 05-06 owners with failed PCMs. PCM from earlier years will not work as the TCM is integrated into the PCM on the 05-06 rigs.
 
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I was wondering about pcm failures as well. Does the failure happen in automatics more often than manuals. Or does it not matter
 
Would it be worthwhile to start a poll? It wouldn't be scientific, but might give us a feel for how common it it. I know my '06, automatic, was replaced, before I bought it. It has Mopar reman unit.
 
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The automatic and manual both use the same PCM. Because the TCM circuit is active in the autos, there’s an additional fail point. They both use an NGC (Next Generation Controller) PCM.

The PCM in my ‘05 LJ had two failures. The first was the ignition sense circuit - the PCM no longer woke up when the ignition was turned to ON/RUN (dead gauges, fuel pump not priming) and only activated when the ignition was in START. This went on for over a year.

The 2nd failure was related to the TCM circuit - the PCM started operating the transmission in extreme overheat mode (TCC lockup in 2nd gear). At first this only happened after parking for a couple of hours on extremely hot days and then driving again. By early summer of this year it was happening every day.

Back in June I replaced my PCM with one from WranglerFix. This resolved both issues.
 
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My 06 auto trans 4L suffers mildly from failure- hard 1-2 shift each drive cycle after being off all night. Overheat trans code plus another code forgotten. Weird 188 degree temp sometimes posted on mirror readout and when that happens also does not show true north on mirror compass. Worse in summer heat. I know Wrangler Fix will take care of it but i have been holding off.
 
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So a PCM failure does not necessarily mean you can no longer drive it? Asking because if I do have trouble with my 06 i have time to order one from USA.
Also why is a manual PCM much more expensive than the Auto PCM.
Cheers
 
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Fishtaco said:
So a PCM failure does not necessarily mean you can no longer drive it? Asking because if I do have trouble with my 06 i have time to order one from USA.
Also why is a manual PCM much more expensive than the Auto PCM.
Cheers
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My rig was still drivable. However, I couldn’t pass smog due to the CEL. I wouldn’t have replaced the PCM if I resided in a community without smog testing requirements.
 
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Hey guys,

I apologize for not answering in a timely manner and will do my best to answer all of the above...

@UND_Sioux Our PCM cannot be tuned or supercharged and will not work with a stroker build...The failure rate on 05-06 TJ's is hard to say. When the issues start occurring, they are impossible to repair. In 2005, Chrysler engineers combined the ECM and TCM together to make the PCM and mounted it in the worst place for heat. A true recipe for disaster. The same issues affect the 5.7L Grand Cherokees, Durangos, Commanders, 6.1L Hemis and 2.4L turbo PT cruisers.

@Tomcat There is no correlation between manufacture date and life expectancy...The OEM part was made by Huntsville and the processors haven't been around for several years.

@Wrebel0728 The automatic pcms fail more often because there are more automatic Jeeps...Manual pcm failures are faulty 02 sensor codes, cam/crankshaft codes and then the Jeep will just die while driving..

@SoCalGlide What year was your pcm re-manned?

@AjRagno Thank you for your testimonial and I am here if you should ever need me.

@Phil Younger Call me anytime and I'll make you an offer you can't refuse just like Luca Brasi!

@Fishtaco . PCM problems do not mean you cannot drive the Jeep. Over time, the issues tend to get worse until the PCM goes kaput. At that point you can start singing Dandy Don Meredith's, "Turn out the lights the parties over!"

Manual PCMs are more expensive because there are a lot less manuals on the road and the scarcity of the part. I see you are in Perth, WA. I listen to Pastor Robert Clancy on YouTube from your hometown on a daily basis!

Hopefully I have answered all of your questions and will do my best to be more attentive in responding to forum posts.

All the best,

Mark
 
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What would prevent me from taking a PCM, TCM, wiring harness, and a 2004 engine/transmission and putting it in a 2006?

This is making me rethink my LS swap options.
 
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UND_Sioux said:
What would prevent me from taking a PCM, TCM, wiring harness, and a 2004 engine/transmission and putting it in a 2006?

This is making me rethink my LS swap options.
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I can’t say...I will run that past my tech and reply in the AM.
 
UND_Sioux said:
What would prevent me from taking a PCM, TCM, wiring harness, and a 2004 engine/transmission and putting it in a 2006?

This is making me rethink my LS swap options.
Click to expand...
Nothing, you could do that pretty easily if you had a donor vehicle especially.
 
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Chris said:
Nothing, you could do that pretty easily if you had a donor vehicle especially.
Click to expand...
I'm pretty much building the engine from scratch, and I'm getting a separate transmission so I figured I'd just dig up the appropriate computers and harness from a wreck. I just want to make sure the gauges work etc.... I'll download the wiring diagrams and compare side by side.
 
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