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greg conte
New User
Mar 27, 2014, 4:59 PM
Post #1 of 7
(1751 views)
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Thansmission wont shift
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2001 jeep grand cherokee
4.7l v8
140000 mi
Transmission doesn't shift.
Code says short on neg. side of solinoids.
I baught and installed a used transmission and trans. compoter that worked in the other jeep.
still had the same problem.
Took the wire harnes off, striped, inspect, re taped and installed. Still had the same problem.
Fuses are good and power is going to the computer.
Is it possable that the main computer is defective?
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Discretesignals
Ultimate Carjunky
/ Moderator
Mar 27, 2014, 5:03 PM
Post #2 of 7
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Re: Thansmission wont shift
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Wow, did anyone actually do any troubleshooting on this one?
What is the trouble code number(s)?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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greg conte
New User
Mar 28, 2014, 9:21 AM
Post #3 of 7
(1705 views)
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Re: Thansmission wont shift
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Thanks for rersponding. Codes are po755 and po750
The guy that checked the codes said there was a negitave short in the trans computer. I changed the computer and we got the same falt code. Then I was told the harnes had a short. I striped the intire harness and found no problems so I replaced it. Same codes came up. I was told the problem was in a transmission solenoid. I changed the transnission, Same code came up, Getting power to fuses and computers. If uou have any ideas I would apprecate your feed back.
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kev2
Veteran
Mar 28, 2014, 10:22 AM
Post #4 of 7
(1698 views)
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Re: Thansmission wont shift
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I will look into and post some ideas-
First- post ALL codes, advise is vehicle is stock...
hopefully you still have the origional PCM?
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greg conte
New User
Mar 28, 2014, 11:26 AM
Post #5 of 7
(1693 views)
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Re: Thansmission wont shift
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The Jeep is factory stock. The registration is 2001 but it was built in 2000. I am a mechanic but Im not in tune to the electronics of solenoid controlled automatic transmissions and I dont have the equipment or the now how to check it. Is it possable the main computer sends signals to the transmission computer? Thats one part I have not changed yet. Ive ran into other problems with vehicles that wonld not come up with an accurate code. My other jeep would run rough from time to time and no codes came up. It turned out to be the ignition switch not making a constant contact on one of the points.
Thanks again for your time.
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kev2
Veteran
Mar 28, 2014, 11:51 AM
Post #6 of 7
(1688 views)
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Re: Thansmission wont shift
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are you seeing the CEL come on?
can you read the P1xxx so called manufacturers specific codes - thinking is look for P1767 but any others may show.
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kev2
Veteran
Mar 28, 2014, 12:05 PM
Post #7 of 7
(1684 views)
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Re: Thansmission wont shift
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and yes they (PCM TCM)surely communicate ... this is a 45RFE so most info is the 4.0L be sure to differentiate. theory is solenoids always have a 12v source from the relay, the other wire* goes to the TCM - it is when the PCM grounds the wire that the solenoid functions, The TCM monitors this signal wire- even when ungrounded- checking that there is voltage on the circuit, AND the issue here is that circuit check.
The Transmission Control Module controls all electronic operations of the transmission. The TCM receives information regarding vehicle operation from both direct and indirect inputs, and selects the operational mode of the transmission. Based on the information received from these various inputs, the TCM determines the appropriate shift schedule and shift points, depending on the present operating conditions and driver demand. This is possible through the control of various direct and indirect outputs.
* terms control circuit, signal wire or switching wire may be used
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