Originally Posted by roddaz
Tonight driving home, 5 minute journey got the eng management light flashing and limp home mode. When cycling the ign key I get Transmission over temp but only for a second.
Are these problems connected ?
This is such a common problem for these vehicles. Here is my take. I have an 06 Overland with 5.7L 4WD. I know it isn't the diesel. I have been chasing the same problem for about a month now.
First thing I started with was the solenoid pack in the trans above the valve body. I've learned that on my vehicle it has a 545RFE Trans which is built by Chrysler. The other trans is the NAG1. NAG stands for New Automatic Gearbox. The trans temp in the NAG1 is part of the governor. It's easier to replace. I had a temporary relief from this trans overtemp issue for about 2 days and it came back. After checking the wires up top at the PCM and at the top of the trans I concluded the wires and connectors were fine. Also checked Ground wires and Positive cables.
Using a LAUNCH CRP 123 scanner I went into the data stream menu under the trans module to monitor voltage of the temp sensor and Temp reading. Driving in traffic, highway speeds and idle. The voltage reading would be steady at 3.xx V and all of the sudden just drop to 0.50 V. When it dropped out the temp went from a normal 170 ish to over 300 in a matter of a second. That is not physically possible for the fluid to change temp that fast.Light back on for Trans Overtemp. That told me that it was related to the temp sensor. In my case the 545RFE has the trans temp sensor included in the solenoid pack. Getting back to what I ultimately did, I replaced the PCM. I used a company called AutoComputer Exchange in Davie, Florida. $169.17 w/ free shipping. Just mail them back your core and you get a one year warranty.
I installed that today and everything worked out until I had to figure out how to perform the re-learn procedure for the TPS. I had the red lightning bolt on the dash. Now everything is solid and I'm hoping for the best. Now the voltage range is more stable and the temp readings are normal. Hope this helps!
There is not enough info on how to combat this issue out there! I have also read that the commander has a no start condition with this issue. They have had better luck by replacing the starter. When the Trans selector is in Park or Neutral it supplies a ground. The starter is on the same circuit. Make sure you find out which transmission you have before proceeding.