[200_S_AWD]

Welcome to the forums. There is a rev-limiter to prevent excessive engine speed in Park or Neutral. That behavior is normal. It should get to redline (above 3000 rpm) in gear and under load.

It is important to use OEM (not necessarily Mopar) parts, especially O2 sensors. I have had issues with Bosch and 'universal' sensors. Mopar gets their O2 sensors from NGK/NTK.

Chrysler uses a speed/density calculation for EFI and doesn't use a MAF. It does use a MAP and the TPS is built-in to the ETC (electronic throttle control):

Electronic Fuel Injection Mass Flow vs. Speed Density- Car Craft Magazine

Once upon a time an engine needed three things to run: fuel, air, and fire.

www.motortrend.com

The P0420 is likely real (the PCM uses the before and after O2 sensors to test the cat). The O2s get tested before the cat. You want to be sure the sensors are telling the truth before condemning the cat. The cat is under the 8yr/80K mile warranty, which you may just be outside of?
If the ceramic honeycomb cat element has broken up or melted down, it can restrict exhaust flow, reducing power. It can also be a fire hazard. Any engine misfire that sends raw fuel and oxygen downstream to the cat, can make internal element temperatures soar.

The 'no ck eng' light is bothersome. If the previous owner knew of the failing cat, he may have snipped the warning light LED to extinguish the light before trading or dumping the car, instead of fixing it properly.

There was a PCM software update. It doesn't address any of your issues, but the car may run better with it (if it hasn't been done yet):

https://static.nhtsa.gov/odi/tsbs/2017/MC-10138911-9999.pdf

 

[200_S_AWD]

It should be in the front. Attached to the black plastic intake manifold with a single screw (you can see the edge of the P/S pump pulley in the top, left corner of the top image).
The connector has 3 wires: Vt/Br, DB/LB and Yl/Pk.

 

[200_S_AWD]

Make sure the radiator fan comes on. You need it at a stop or moving slowly. Going down the road, enough air is blowing through the radiator that you shouldn't need the fan.
Turning on the A/C should bring the fan on also, as it has to cool the condenser in front of the radiator.

You may need a cat? If so, look for an inexpensive 'direct fit' as long as you don't live in California, NY, ME or CO:

Davico® - Direct Fit Catalytic Converter and Pipe Assembly

Catalytic Converter and Pipe Assembly by Davico®. Converter Configuration: Direct Fit. Position: Center. With 2 O2 Sensor Ports. Catalytic Converter Overall Length: 38.75". Davico 19393

www.carid.com

 

[200_S_AWD]

The 'ck eng' light should work if it passes the bulb check at start up. Has the previous owner modified or hacked the PCM in any way?
You should be able to 'make' the light come on by unplugging a sensor or relay (A/C for example?) and then start the car.
If you erase the P0420, it will usually take 2-3 days to set the code again. It shouldn't come back right away. Are you sure that the scan tool is erasing the code?

 

[200_S_AWD]

i have done all that but you have it right on money thats excately how its doing , after the p0420 code as i explained in my first statement on here u will see everything i have done i have replaced both 02 sensors, i have replaced the crankshaft sensor i have replace the throttle bottle controller brand new and i did reset it i pulled the 10 red fuse out and left out for a hour and then put back drove around cleared out the p0420 code every time before i done it and and we just replace the map today and still same thing , we even took out brand new air filer and it got louder but we know no vacumn or exhaust leaks we checked that too , yes i was told there is no tps the map i guess took its place and yes this the only car to my understanding as i was informed that does not use the air mass flow sensor its built i take it into the throttle body controller , how did u reset yours may i ask ? but you are right we cant get it above 30 mph and running at 3000 rpms till it finally goes but never above that mph or rpm as i just explaned and yes your right it does jerk slightly at times not much mostly it will not accereralte it just stalls out like it dont wanna go strange to me and i dont have no check engine light on at all never have. we just got the code from code reader p0420 any ideas, and most fuel pumps last 15 years but again no code for that or check engine light i dont get it and for about 3 to 4 seconds when u put more gas into it it rattles till u let off strange. any ideas? thanks for your input , your right on everything it does, i thought the map was gonna fix it, it didnt

I just saw this in the other thread and brought it over here. A battery disconnect or fuse pull used to reset computer memories and erase fault codes in the old days, but not on newer cars. Any reset has to be done with a scan tool.

The 'rattle' on acceleration is not good. It could damage the engine. Does the car have the correct spark plugs in it? What color are the tip insulators? Are they black (rich) or white (lean)?
If the cat is broken up inside and restricting exhaust flow, it will do as you describe.

 

[200_S_AWD]

A P0420 shouldn't come back quickly. It should take at least a couple of days to retest and set the cat code.
Spark plug color may help in diagnosing a fuel or mechanical problem. The plugs should be either Champion RC12MB3 or RC12MC4 depending on which 2.4L you have. There was a standard LEV (low emission vehicle) and the PZEV (partial zero emission vehicle). Having the correct plugs are an important starting point.

The PCM may have a problem if it can't turn on the 'ck eng' light (we know that the light itself works). If you can get to a parts store, try their customer-use code reader to see if you get the same P0420.
Some generic code readers may not work right on all OBD2 cars.

Save your money, don't keep replacing parts until we can get a handle on what the car actually needs.
Do you know any of this car's past history from the previous owner?

 

[200_S_AWD]

Welcome to the forum. I have used aftermarket 'direct-fits' on other cars with good results. My own Neon needed one about 15 years ago.
Back in the '80's we had 'universal' cats that was just the cat, we had to weld or clamp and bend pipes for them. They were a pain. The 'direct-fits' just bolt and clamp in like the original. Save or replace the under-floor heat shields. They are important.

Being an emissions device, it has to be certified by the EPA. CA has stricter regs and its own state emissions CARB which must certify any device. Many aftermarkets cats say 'Not for sale in CA' as CARB (California Air Resource Board) wants OEM cats in most cases.

It is important to know why the original cat failed. Engine misfire and rich fuel mixtures, etc can overheat a cat and damage it.
The upstream & downstream O2 sensor readings are compared by the PCM to 'test' the cat effectiveness at regular intervals. If an O2 sensor fails its test, the PCM won't bother to test the cat as the results wouldn't be valid. The cat is the last device tested, as everything else must pass first.

Fix these problems first or else the replacement cat may also be damaged.
The original cat functions are covered under an 8 yr/80K mile Federal extended emissions warranty in the U.S.

Is your 2014 a V6? There was a TSB# 18-102-16A released for false code sets that can fault the cat (and/or O2 sensors) on either bank.
Make sure that your PCM has this software update before believing a cat code is real: