larryl

You could swap the injector to another cylinder and see if the other cylinder starts misfiring.  Then you'll know for sure if it's an injector before buying a new one.  If the misfire doesn't move after swapping the injector, then try swapping the coil.  I've seen bad "new" ones of these.
 
I've had a few of the 3.6 engines.  I've had misfires due to the wiring harness.  In my case, the injector harness was not plugged in tight to the upstream harness.  I've also had a misfire caused by a bad ECU.  I was able to purchase a used/pre-programmed ECU online for a reasonable price.  I had one engine with a persistent misfire that ended up being bad piston rings.  A pressure leak-down test found that one.  The 3.6 engine is also susceptible to the rocker arms issue.  I've had this issue and it didn't cause a misfire condition because I caught it early enough, but I've read cases where it can cause a misfire issue.
 
I'm not trying to scare you here, just listing some other causes of misfires that I've personally seen.

Not sure of what you are saying IS in your Journey. I surmise you have the 8.4" screen "infotainment" display. IF when powered on and there is NO NAV. ICON PRESENT. then you do NOT have the radio module that has the Nav. capability. It is NOT a function of the screen and likewise for the audio. there is a radio module buried in the center of the dash. 
 
So in "layman's" terms, if you want nav., you need a different radio module. And YES this subject has been discussed many times on the forum.

Or to say they are junk and never buy one

THIS is a common problem when people ask for help and then when they get the problem fixed they usually never come back to post the fix for the problem thus leaving others wondering on what to try,please repost when you find your problem solution

Most aftermarket complete struts are "one size fits all", the ride height difference is from the SPRING rating and not the strut. 
IF you just installed them, give it a couple weeks to "settle in" as the ride height will probably lower down some. 
The Traction control light and loss of cruise is from a damaged wheel speed sensor. Auto parts stores will pull codes for free{resist buying needed parts from them...unless price is good},to tell you what specific corner the problem is on.

I programmed both my '14 and '11 for new fobs AND activated remote start with the new RS capable fobs using alphaobd software program. I learned how by Google search that came up with a youtube video on a Ram pickup truck. Quite similar for your needs as this worked for my learning how and being successful.
 
Details of your cars trim level and just what level fob you want to program to your car are lacking for better responses.

just connect the 1 hoses that deliver the hot coolant to the core with the return hose to the rad / engine from the heater core, i am sure you can google it or even better check on you tube for more info and videos 

For the benefit of you and others seeking advice/help in correcting a warning light{CEL/TCS/STAB. CONTROL/ etc.} it is necessary to post the actual codes and NOT description of code{s} IF they have them. Most major parts stores will check most system codes for free if a scanner is not available to the person involved with the vehicle. There ARE diagnostic steps for each and every code beyond just throwing in a replacement senor or part. For responders to be able to give good assistance , they need the actual code number so these steps can be suggested.
 
Please also remember the vast majority of members here are vehicle owners and not automotive technicians, some of us do however have that type of background, 
So the better the background info posted of a problem will get better responses.
Good luck and keep us "posted" on your "journey" in keeping your GF's Journey working properly for her!

If you have Bluetooth (Dodge term HFM-hands free module)
pull the fuse. 

Great news if it’s running and no limp mode issues.

Not to be the bearer of bad news, but….The 3.5 v6 is a timing belt interference engine, unfortunately. Usually by 100k the belt and idlers should be replaced. Most people push it quite a bit farther.
Not a typical diy job, If it  jumps or breaks, the engine is usually toast. If it’s not done you will need to start investigating getting it done. Labor part can be several hours for a mechanic, water pump change also makes sense at same time since it’s behind the timing covers. 

To combat the somewhat floaty boaty cozy recliner feel of the r/t awd rallye model  i went all weather agressive with the cross climate 2's. Size was stock 225/55/19. I previously was driving on bridgestone dueller h/l's all season tires which were i experienced to be, really really, bad tires....Im literally glued to the road now. Its transformed my driving experiend to tight,taut, and responsive. Best tires ive ever owned.

With the circuitry and many modules to control functions, you really need to have a good scanner that can also read body control module{not just basic OBD} functions and codes They used to be a bit expensive a few YEARS ago, but are now pretty reasonable in cost. Knowing what CODES are at issue is 90% of the battle. I've found that poor wire connections and poor grounds are the true culprit to many problems, BUT trouble codes being retrieved and diagnosed shorten the figuring out process dramatically.
With what you have posted, any responses for "look at's" or fixes is just GUESSING,
YES TCS warning MAY be a bad sensor but it could also be a hub bearing going bad as part of the wheel sensor components{tone ring} are part of the bearing assembly.

a tire with a few pounds low will not put your journey into limp mode,sounds like you might  have an electrical problem,also you could be having a problem with a wheel speed sensor. or maybe a wheel bearing going had,, hence the traction light

Heater core ,head gasket, plugged rad, bad water pump, no coolant could all be why hope that helps

lol, so much info ,,,would suspect your thermostat more than anything else

Welcome to the group...... when asking about a problem we need all the info on what you drive and all the problems with what things you have done to it to be able to even guess what might be wrong.....there is no 3.7 there is a 3.6 so who is changing the spark plugs every 6 months? they are good for 100k and it takes a considerable amount of time to even get to them. also are you using the OEM plugs ? . just saying.. oil changes should be around  every 7 k with just regular driving ,heavy use driving should be done even sooner,, what about the trans service has any been done? and dont forget the awd maintenance and coolant services. YOUR best option is to have it serviced when the light is on at a dodge dealership to see the code, they would have the best info on what they think is wrong and might end up cheaper than unloading the  parts cannon on your journey. please report back on what you find out is your problem for others to learn from it

Thermostat installed correctly on the new engine?

2009 had a 3.5 engine, so what temp is it going to ? are the fans coming on? are you using coolant mixed right? sounds like you need to return too who ever changed your engine out before you overheat it

Here was my problem a new harness fixed all my issues

check out YouTube videos on sunroof drains and how to clean them out...here is what you should be looking for this one is on a caravan but should almost be the same setup as most SUVS..........REMEMBER YOUTUBE is your best bet for info on how to fix your journey or anything else
 

To transfer ownership vehicle needs to be certified by the dealer he mentioned. Everything has to work , for 36 days I believe.
Just bring it back.
 
DTR Wont come on if parking brake used and remote start is used.  Could check front yellow signal bulbs. They are two filament bulbs (like 1157 brake light)  with direction signal flash and running light on separate filaments. But are yellow coloured 1157.
Some cars use main head light bulbs on lower power feed via a separate DTR module. Journey doesn’t.

ALFAOBD can be used to turn on day time running lights feature in the ecm.  Lots of U.S. guys have done it as an extra safety item. Feature not on dash display controls, or at least not on my 2014 or daughter in laws 2012.

Can't tell from your picture, but does the car has the sunroof option? IF it does, then I'd suspect the drain lines are clogged with debris, a common issue with all factory sunroof cars.

Check the fuse.

Could it be a coolant line has ruptured do you have the rear heat option in the vehicle? A 15 Journey could have 2 or 3 rows of seats

You are already there. You originally posted in the Forum Help and Suggestions section which is reserved for Q&A on how to use the forum, not specific technical questions.