Hi, welcome to the forums.

You didn't mention which transmission you have or how many miles, but from the sound of it (no pun intended) you have the CVT.

The CVT fluid fill tube is pictured below. If you don't have this fill tube then you have the 6 speed automatic and you can skip over the CVT info following the pic.

As you might have read, on the CVT, the fluid and both filters should be changed initially at 30k miles, then 30-50k miles thereafter depending on driving conditions.
The service manual says 120k but that is far too long.

Dirty fluid and filters can cause whining, transmission overheating, and limp mode along with pressure related codes (p0777, p0746) and if left unchanged for too long can result in damage to the transmission due to scoring of the valves / valve bores from small bits of metal.

The fluid and filters change will run around $350+ at a dealer, independent shops might charge less, or you can DIY if you're mechanically inclined.

More info on CVT fluid and filters change here:

CVT updated pan, dip stick and cooler links please

Been done to death but I cant find all info with links etc to know i'm on right track. Want to service the CVT (replace filters and fluid) also have seen this 4 ports CVT Transmission Oil Cooler, 2 for Engine Coolant 2 for CVT Fluid. 2 pipes for the inlet/outlet of coolant 2 pipes for the...

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Code p0420 relates to catcon performance, an O2 sensor problem or possibly an exhaust leak.

Codes p2128 and p2123 are related to the accelerator pedal position sensor.

Codes p0123 and p0222 are related to the throttle position sensor.

Code p0108 relates to the MAP sensor.




One thing that can cause a lot of codes all at once (that are seemingly unrelated) is bad connections at the two engine bay grounds; G110 and G111 / G112.

These two ground nodes supply grounds for numerous things including the PCM and sensor grounds, like the O2 sensor, MAP sensor, the accelerator pedal position sensor, and throttle position sensor.

The wires on these grounds can corrode under the eyelet crimp and insulation where it can't be seen.
The fix for this is to cut off the old eyelet, strip back the wires to good metal, and add a new eyelet.

More info on the grounds and what connects to them here:

G110, G111, and G112 ground location and wiring diagrams

G110 G111 & G112 G111 G112

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Some of these codes could also be caused by the PCM, either by it failing or glitching.


What you might try is clearing these codes and or resetting the system by disconnecting both battery cables, touching them together for 10-15 minutes, reconnecting them, then see what codes come back.


Also, check your battery connections and make sure they're good and clean.

 

Thanks so much for the info! I do have CVT but it’s an automatic. It has 160,000 miles.

Just an update…yesterday he blew air into the transmission fluid again for several seconds. And it started accelerating! All but 3 codes are gone (don’t know which ones are left). We both drove it around the block a couple of times. Then I drove it about 30 miles to a friends house…..its still there. Won’t accelerate again. What about blowimg air in the transmission fluid causes it to accelerate??

 

Aside from what I've already mentioned, I would consider taking it to a Jeep dealer or a transmission shop that is knowledgeable on Jatco CVT's for a full definitive diagnostic.