2025 yukon AT4 ultimate trans overheating at idle

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GJAngerer

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Thanks for the input and the comparable information, I really appreciate it.
I contacted the dealer yesterday and the ecu had a U0102 code on it.
"Lost Communication with Transfer Case Control Module"
@genestoy those coolant and oil temps seem like they are on the very high end of normal limits.
 

jfoj

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I would also be concerned about the 13.2 MPG Average Fuel Economy as well!

You have a Diesel and unless this thing was idling in gear for a LONG time and the vehicle has not driven anywhere since the Fuel Economy Average was reset something is off here.

My 6.2l gas Yukon has a Lifetime Average Fuel Economy of I think 17.6 MPG.

Something is clearly wrong and it seems the temperatures may be somewhat in agreement?

The Diesel has an external transmission cooling thermostat. I also recall a GM bulletin about kinked cooling lines in the back of my mind. I will see if I can find out if this is a correct recollection.
 
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GJAngerer

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Yes my wife was sitting idling waiting to pick my son up and then sat in a drive thru for a while. We took a trip out to Palm Springs and got 31mpg.
I understand the temps being high when it's 100 plus out, but the day this happened it was 82°F outside and she was idling.
I'm still waiting to here back from the dealer, but I'll post something when they get back to me.
Thanks everyone!
 

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