TJ: What you think is a transmission problem may be a PCM problem: UPDATED 8.8.2014 - Great Lakes 4x4. The largest offroad forum in the Midwest

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Old July 11th, 2014, 03:09 PM   #1
Bullhed78
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Default What you think is a transmission problem may be a PCM problem: UPDATED 8.8.2014

I bought a 2006 LJ with a 4.0L and 4 speed auto back in February with 115,000 miles on it. I drove it home from Florida and everything seemed to work fine other than the overdrive was a dog with 33's and the stock 3:73 gears.

Approximately a month after I bought the jeep I started getting this weird noise from the transmission. I sounded like hungry baby birds chirping. The jeep also had low torque but never had any shifting issues. I changed the fluid and filter (yes, I used ATF +4). I also installed an external trans cooler and trans temp gauge. This did not fix my problem although it gave me piece of mind having the cooler and temp gauge. Eventually I took it to a reputable trans shop and they informed me that the torque converter was bad and the transmission had been overheated at one point or another. I had a complete rebuild done on the 42RLE transmission. What I'm about to describe isn't what was causing this particular issue.

Approximately one month later and maybe 1,000 miles on the fresh trans I start getting this weird shift going from first to second when the jeep is "cold". What I mean by "cold" is if the jeep sits overnight or for several hours it shifts funny. After I drive the jeep and it goes through a couple shift cycles the problem went away. I returned the jeep to the trans shop that did the work to have it fixed under warranty.

They drove the jeep and felt the issue but could not find anything wrong with the transmission. They got one of their top techs on the job and found the problem is not with the transmission but instead is a PCM problem. To confirm this they let the jeep sit overnight. The next morning the tech hooked his scan tool up and took the jeep for a ride. Of course it made the bad shift and the scan tool caught it.

I did some research online last night and found that this seems to be a common problem with 2006 jeep wrangler LJ / TJ. A lot of people spent a lot of money chasing a ghost. The PCM doesn't throw a code so there is no indication it is bad. People talk about heat sensors showing crazy high temps so they change them only to have the problem return. They change solenoid packs only to have the problem return. They have transmissions rebuilt or replaced only to have the problem return. What I found people that changed the PCM to an updated PCM from a reputable company (ie: Chrysler) solved their problem. People that bought PCM's online seemed to be hit or miss but mostly miss.

The trans shop called the dealer today to order a PCM and they are on national backorder with an approximate seven day wait because this has become such a common problem. Chrysler knows there is an issue but there is no recall.

I know this is long winded but if I can prevent someone from chasing a ghost and throwing a lot of money at a transmission that isn't the problem than this post is worthwhile.

UPDATE 8.8.2014: I got my jeep back on July 18 and it is driving and shifting perfectly. Although I did not have any check engine lights or anything my jeep had the following codes in it P0218 and P0714. The final diagnosis was a bad PCM which was replaced with a Chrysler remanufactured unit. Apparently if you get a brand new unit it is prone to the same problem I was having but the remanufactured ones have the updates that are needed. Anyhow, the jeep has about 1,500 trouble free miles on it since the repair including a trip to the U.P. and back.

Last edited by Bullhed78; August 8th, 2014 at 09:06 PM.
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Old July 11th, 2014, 03:57 PM   #2
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So, what was the whistling noise at idle all about then?
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Old July 11th, 2014, 04:31 PM   #3
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Quote:
Originally Posted by Gogolen View Post
So, what was the whistling noise at idle all about then?
That noise was a bad torque converter and had nothing to do with this problem. I only included that info to express the reason why I had a brand new transmission in my jeep. However after reading about other people that had this same problem with the first to second shift that replaced transmissions only to find out that was not the problem I wanted to give people a heads up.
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Old July 12th, 2014, 11:00 PM   #4
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I have a LJ with the same issue on the one two shift when cold. I have a Trans guy lined up that was going to plug it in and check it. He was thinking it was a solenoid sticking but didn't know without checking.
I could see the dollar signs in his eyes.
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Old August 8th, 2014, 09:04 PM   #5
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Update: I got my jeep back on July 18 and it is driving and shifting perfectly. Although I did not have any check engine lights or anything my jeep had the following codes in it P0218 and P0714. The final diagnosis was a bad PCM which was replaced with a Chrysler remanufactured unit. Apparently if you get a brand new unit it is prone to the same problem I was having but the remanufactured ones have the updates that are needed. Anyhow, the jeep has about 1,500 trouble free miles on it since the repair including a trip to the U.P. and back.
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Old August 9th, 2014, 07:31 AM   #6
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Check with dealer for an update on PCM . Might just need a flash update as we do a lot of flashes on pcms for shift issues and engine issues
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