Jeep 2012 trans issue and check engine light

hey all, I am new to Jeeps.net. I am a car guy and have built Chevelle's and Camaros but not a jeep yet. I have a 2 questions and was hoping that someone has experienced these and can offer some guidance.

1. possible trans issue:
I recently bought a 2012 JK (1 yr ago) and I had a 3" lift and 35" tires installed. About 3 months ago the jeep started to with a slight "hiccup" once in OD at 35-40mph. It is random and feels like the car wants to down shift and then back up shift. it feels like a slight bump from behind.

I have had it to the dealer and they flashed the TCM etc. but no resolution. flashed the OBD to correct the speedometer thinking that the computer was conflicting with the shift pattern with new tire size, but no resolution.

2. check engine light:
the other day I was driving and the check engine light came on and total loss of power. I could only go 30mph and I had the gas pedal to the floor. it had a total loss of power and felt like I lost 3 cylinders. I pulled over and turned the car off and waited 20 seconds. I restarted the car and the check engine light was gone and the car ran fine. I put a scanner on it and there was no error codes....hmmm

any thoughts?

 

Welcome @beni07 ...too bad the dealer with pro scanner couldn't have retrieved some codes. Larger tires can affect AT shift points which should be addressed with programmers like flashcal/procal/jscan. If there is an actual trans issue getting codes from the TCM could point at 3rd or 4th gear pressure sensors.

 

I am thinking if the CEL was on there is a code, maybe your scanner is not capable ?
Might need to check Pending or history files.

Could the bumping in and out be a TCC issue - is there a slight rise and drop in RPM associated with the bump?

There is NO programer, chips or a device plugged into DLC?
Other than 3" lift and tires nothing else changed or modified?

 

Thx @aggrex for the help. I have upgraded with flash cal programmer for tire sizes etc.

@Awrench i did take it to the dealer and the could not retrieve an error code. Also there is no rise in RPM when the “bunt” hit between 4th and OD.

 

I spoke to a buddy that was a mechanic for 40 yrs and he thinks that the throttle body may going bad

 

the system is electrical and it has a diagnostic series of codes, the issue is we are not seeing any codes.

Do you ever see the elec throttle symbol illuminate?

 

Welcome @beni07 . Good luck.