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There is a service Bullentin you should be aware of. The vehicle will most likely have to be scanned with a reader to find the issue, at least now you are aware of the bullentin which should be taken care of if it is the issue, I hope this helps.
The vehicle's automatic transaxle (ATX) may exhibit shift shock while the engine warms from cold to normal operating temperature. The symptom is intermittent, it does not occur all the time. The shift shock usually occurs during 1-2 or 2-3 upshifts, or 3-2 part throttle downshifts.
In most cases, the cause of the shift shock is from the TRANSMISSION CONTROL MODULE (TCM) software calibration. A new software calibration is available on ESI to correct the shifting concerns.
Customers having this concern should have their vehicle repaired according to the following repair procedure.
Inspect the vehicle for a "Port Campaign" rework sticker affixed to the underside of the hood.