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42re tcc issue


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comanche
Novice

Nov 18, 2017, 7:42 AM

Post #1 of 12 (584 views)
42re tcc issue Sign In

After extended driving tcc will not relock at hiway speeds. Should speed drop well below initial lock up then be increased above 48 mph will again lockup and stay locked but not relock if driving conditions force the tranny out of lockup. This condition rarely occurs in local driving but mostly only on longer trips and is aggravated by hills and busy traffic. On a recent trip to the mountains of NC, I noticed when climbing a grade, the tranny would lockup out of the blue, just when it was most unneeded. [vacuum related?] There are no codes set and because this doesn't happen locally, I don't know to get it diagnosed.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Nov 18, 2017, 8:47 AM

Post #2 of 12 (575 views)
Re: 42re tcc issue Sign In

Year, Make, Model and trans type would help some.
Highway? If under a load, hills it's not supposed to lock up and other reasons,


T



comanche
Novice

Nov 18, 2017, 12:09 PM

Post #3 of 12 (558 views)
Re: 42re tcc issue Sign In

Per the title, the transmission is a 42re in a 2004 Jeep WJ, 4L, 4x4. In as much as this is electronically controlled, I'm thinking this is a PCM or sensor failure.


Hammer Time
Ultimate Carjunky / Moderator
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Nov 18, 2017, 12:24 PM

Post #4 of 12 (551 views)
Re: 42re tcc issue Sign In

Gary (gsferraro) is a trans shop owner and should be along shortly with an answer for you.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



gsferraro
Enthusiast

Nov 18, 2017, 12:33 PM

Post #5 of 12 (544 views)
Re: 42re tcc issue Sign In

Hello, Nothing is controlled by vacuum on this trans, when lock-up occurs you will see the rpm drop by about 200. Is this what your seeing, a fluctuation of about 200 rpm? Gary


comanche
Novice

Nov 18, 2017, 12:40 PM

Post #6 of 12 (540 views)
Re: 42re tcc issue Sign In

Yes, it seems to work fine [seldom failing] in local driving, but on longer trips it will begin to fail to relock after from as short as 100 miles, sometimes it goes as far as 500 miles, depending on traffic conditions.


gsferraro
Enthusiast

Nov 18, 2017, 3:16 PM

Post #7 of 12 (530 views)
Re: 42re tcc issue Sign In

If you have access to a scan tool that shows live data, you can look at inputs, the computer commands lock-up when certain conditions are met, goes by inputs to pcm like engine temp, trans temp, vss, throttle position. Anything going on with the engine on long trips does it seem to run hotter than normal? Gary


comanche
Novice

Nov 19, 2017, 5:43 AM

Post #8 of 12 (517 views)
Re: 42re tcc issue Sign In

Gary: Thanks for working on this. I have a live scan tool but have never carried it on trips but engine seems to always run fine, locally or on trips. Because it was inexpensive, I replaced the tps but no change. I thought that the unexpected lockup going up hills might indicate some sensor failure related to vacuum but no mil codes have ever appeared.


gsferraro
Enthusiast

Nov 22, 2017, 6:49 AM

Post #9 of 12 (484 views)
Re: 42re tcc issue Sign In

Hello,
Maybe try cleaning the mass air flow sensor, i had that once but on a GM car, the tcc was cycling. Gary


Discretesignals
Ultimate Carjunky / Moderator
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Nov 22, 2017, 9:18 AM

Post #10 of 12 (468 views)
Re: 42re tcc issue Sign In

Hey Gary, there is no mass air flow sensor on that model.

Looking at inputs would be a good idea to see if the PCM is actually commanding the tcc apply.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Nov 22, 2017, 10:58 AM)


comanche
Novice

Nov 22, 2017, 10:39 AM

Post #11 of 12 (458 views)
Re: 42re tcc issue Sign In

I think this 2004 6cyl has a MAP sensor. Can I assume that it could have the same effect as a MAF on the transmission.


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Nov 22, 2017, 11:06 AM

Post #12 of 12 (454 views)
Re: 42re tcc issue Sign In

MAP sensor is a critical sensor that the PCM uses for transmission pressure control/ shift timing. You really should start by looking at the transmission data stream information to see how the PCM is commanding the TCC when the problem is occurring. That would give you a direction in diagnosing your issue.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.






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