Another update to this saga. I got a transmission trouble code again, this time it was the speed sensors. So I got two speed sensors from dorman online. Changed the speed sensors and still had problems. If you read this thread you know I made a hack on pin 54 of the PCM to set the temp because I could never figure out my temp signal problem. As you may know the the speed sensors are connected to the tranny temp sensor circuit as well. The speed sensors didn't help and when I went to start the jeep it threw 13 engine codes just after starting and died. I thought I blew my ECU. Found I did blow the ASD fuse so replaced that and still had the tranny codes. Then I found the entire problem to my issue in a grounding out wire harness next to the A/C accumulator, see pic. This was causing the ASD to blow and the erratic temp sensor signals. I removed my hack to the PCM and proceeded on.

WARNING: The dorman replacement parts are junk, they do not have a big enough magnetic core to drive the ECU speed signals. I could not get the speed sensor codes to clear until I put my factory sensors back in. I even ohm out the new and old sensors and they were the same. The dormans are lighter though. This is the second time dorman parts have burnt me, their Tire sensors don't work on the jeep either! NO MORE DORMAN PARTS for me. Jeep is working perfectly again.

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Purchased 2006 LIberty CRD 82K 01/16
SS Cat Back Exhaust, Full EGR Delete,Provent, Michelin 245/70 R16 AT/2
Stock Tune, Serpentine Belt Service,160 Amp Alternator
10/17 96K, New Head, Injectors, ARP Studs, HDS T-Stat
04/18 99K, New Reman Trans
09/18 104K, Lift Pump
01/19 106K, OME Lift, Eaton TruTrac LSD in new rebuilt diff

I've generally found this to be the case as well, I avoid their stuff unless it's the only option.

Hi,

Thanks for your thread in this forum, very interesting.

I'm a french WJ Owner and i'm really interested by your "Hack" of the TCM.
I'm quite sure i'm having the same issue with my 02 4.7 WJ ! I have hard shift between 2/3 in the morning, unless i put more gas, and also rough between D => N or R => N when hot. Everything else is fine,no code, and all my Gearbox sensors are Mopar brand new ones !

Could you explain how to make my own Hack to test it please , as you explain here :
"I made a voltage divider out of two 20K Ohm resistors and connected it to pin 54 on the TCM"

I'll also try to test my sensor ground (pin 23), try to find pb on wire ...

Many thanks from France !

Tony

Check the harness, clean the connector.

You connect two resistors of equal value end to end. One end connects to chassis ground, the other end connects the wire that connects to pin 54 on the TCM. From where the two resistors connect in the middle (hence the divider name) that connection gets connected to pin 54 on the TCM.

Now I thought I had bad thermistor in the valve body but I changed that so I tried the divider to low the temp signal but the whole time that wire was shorting on and off to ground.

Do you have a scanner that lets you see your transmission temp in real time? If you don't have an check engine lights then I think you have a different issue such as wore clutch packs... If it's a 545rfe then you may try to "Re-Learn" the transmission with a good scanner. That resets the clutch pack volumes to account for clutch wear.

Good Luck

_________________
Purchased 2006 LIberty CRD 82K 01/16
SS Cat Back Exhaust, Full EGR Delete,Provent, Michelin 245/70 R16 AT/2
Stock Tune, Serpentine Belt Service,160 Amp Alternator
10/17 96K, New Head, Injectors, ARP Studs, HDS T-Stat
04/18 99K, New Reman Trans
09/18 104K, Lift Pump
01/19 106K, OME Lift, Eaton TruTrac LSD in new rebuilt diff

Thanks for yiour quick reply.

My connector / harness is clean, everything look in good condition.
I don't have DRB3 tools, only a simple OBD scanner that doesn't allow me to view my transmission temp. I have no error code with this tools. And everything is running fine when i drive. I think, it's like this since i bought it, something like 40 000 miles.

Thanks for your explanation on the divider, i'll try it as soon as i can. I'll also try to test my ground on both speed sensor, it could help to find an issue on this ground wire.

For the last point, i've read somewhere that it's possible to reset the transmission, to "Re-learn", without any drb3 tools... Will try it also !

Have a similar problem with an 05 Cherokee (Liberty) that only occurs when vehicle is cold, around 18 deg C where I live. When the car warms up to operating temperature, I clear the codes, temp sensor and/or MS solenoid faults, and the car is right until it cools again. Was going to check the Gateway module near the battery box, but so far have not. Will check earths as a first step. Have changed TCM but still same predictable problem. Sometimes in hot summer weather, the problem may not occur for weeks, but in cooler months it presents on every start up.