Maybe related, I got rust on the ignition key housing.  Had to take it apart to clean it up, lube it back up and everything works now like a charm.  Every now and then I spay son WD40 in there just for good measure and I have not had the problem reappeared.

;)job is done ,i have back up lights now .thanks for help

Show us pictures, I would like to do the same.

I have never ever tried a EPS system on any ATV.  This is my first and only one so far.  I am curios to see how much the EPS helps on driving the machine as even though it is the smaller they make, it is quite a heavy machine weighing at 350 to 380 KG.   Most of the riding I do is actually off-road and I can manage, but, there are a few times when the front differential is locked,  the ATV basically goes wherever it wants to as it is very difficult to steer it.   Like I said I would like to experience EPS and see what it does.

Yeah so I whet the cheap way getting bolts and nuts from an online specialice faster retailer, not the cf moto brand, but the exact same measurement and threat pattern so total for all nuts and bolts is $15.  The expensive parts, from Aliexpress as follows including shipping: Steering arm ($72),  Motor or main unit ($444),  Controller ($375) some brackets and spacers all together ($75).  So all in total it comes out to be $981.79 hahaha I do have a lot of time to go online and fantasize about buying all these parts.  Seems like the installation would be pretty easy and done in a day for sure.  I would put the ATV on jack stands and remove the front tires.  I already removed the wheel wells a long time ago as it makes the washing process a lot quicker.  Just to have more room to move around I would also remove all front plastic parts and maybe even the gas tank.  That is basically it since the ATV is prewired it would be a matter of just plugging the controller and main unit, and changing the long steering arm for the new short one that connects to the EPS motor.   
 
I did checked on www.cfmotousaparts.com for all the original OEM parts including nuts and bolts (some of which show as backorder that would ship in 2 or 3 weeks) but even with the name brand parts it came up to a total of $1675.20. There is also a kit sold by them but I'm not sure what comes in the kit other than the main unit and controller but even if it is just those two parts you get a bit of a discount an the total goes to $1502.45 
If money was not an issue, I would much rather go with the reputable seller even though it would take longer to get all parts and I would definitively wait to have all the parts delivered to start the installation.

At the moment I am unemployed.  The minute I get a job I will pull the trigger an add eps to my 450L.  Have checked all parts needed ant it all will be less than $1000 USD.   Now I just need a job or a contract lol.

Had the same issue a while back and it turned out to be the very little dc motor that engages and disengages the 4wd.  Replace the motor inside the assembly and all was back to normal.  Had a somewhat difficult time finding a dc motor that would fit, but at the end it was a cheap and easy fix.

Check this video where you can see the little dc motor inside of the assembly.  That was the only thing I replaced.
https://www.youtube.com/watch?v=raCNbin-i64

This is if you want to replace the entire thing
https://www.youtube.com/watch?v=HL-JW__NprU

After further investigation, pretty sure it is doable and a case of plug and play per se.  However you'll need all the parts that are quite a few.  On the left side of my machine, there are 2 plus that I'm pretty sure are used for the EPS module.  There is also a bracket to mount the control unit... see pictures for reference.  The not so easy is thing is that the steering column is just a one piece long rod that would need to be replace.  In total a lot of hardware plus the main unit and the controller.  Compare the 2 diagrams on how simple the 400 with no EPS is vs how many more pieces the 500 EPS has.  Certainly doable but expensive.  If I had the money and was in the USA I'll for sure will try this specially because if anything fails,I would  already have all the parts to go back to non EPS.   

Maybe I just wait on flotownj to do his conversion first.

So I am not an expert nor do I claim to know how an atv works....I'm good with tools and can follow directions mostly from NMKawierider, you are the man!   That said, looking a bit deeper and comparing diagrams between a 2020 Cforce400(with no eps) vs the Cforce500(with eps) it all seems like good news.  The voltage regulator is the same on both machines, part # 0800-177000-10000. Also the stator is the same for both quads, part # 0GRB-032000-10000.     Now to my understanding that means that the Cforce400 could theoretically cope with the power requirements to run the eps system with no further modifications. 
Now this is a questions; the ECU is different for the 400 vs the 500 but I suspect that does not matter as that ECU has no role controlling the steering right??? ECU only deals with everything engine related, fuel system, rpms and all that magic right?     

Working on my machine I noticed there were some electrical plugs that are not used on the front of my 400.  I can't recall how many plugs but will check and send pics.   Hopefully everything is pre-wired from the factory and a drop in eps can be used.   

Oh man you guys got me going again....déjà vu hahaha.  Looking at diagrams it seems it would be a direct fit if you just purchase the parts.  There is this kit but with no pictures nor description so maybe give them a call:

https://cfmotousaparts.com/product/eps-kit-cfmoto-oem-9gq0-106000-20000/?srsltid=AfmBOoqScad3pjiW-iXnyVBvkTEpWYWkI8fAJGX8HL0nVsW65DhIyBvL


Also just from YouTube apparently Main Street Cycles in Mississippi moves quite a lot of CFmoto atvs and they have a lot of parts and knowledge....maybe get in touch with them.  I would but I'm in Ecuador and that limits things a lot.  www.mainstreetcycle.com

And that is if everything fits without modifications.  You have a lot of parts, a ton of labor and no guarantee it will actually work.  That is why I played it safe and gave up before starting.

I tried that on my 2020 450L and when looking at the parts even thought they seemed to fit ok, I was strongly discouraged to do the conversion specially because of the higher current stator so I listen and gave up on the project.

My 2020 Cforce450 did the same thing pretty early and I was told it was a bad electric motor or servo.... this piece. Anyway this was replaced under warranty and everything was back to working order.    Good luck with it.

https://www.amazon.com/AYYDXRK-Replacement-Differential-CFMOTO-Q830-314000/dp/B0DHKGHRDN/ref=sr_1_1?crid=1R9I86RI2UUSL&dib=eyJ2IjoiMSJ9.j9goUyh-gEHlyvZIQhWHaQ.R3HkY561bpEH288flwiYWYdLjas1QyfCk8VSBUFmXfY&dib_tag=se&keywords=cforce+450+diff+lock&qid=1752901960&sprefix=cforce+450+diff+lock%2Caps%2C161&sr=8-1

Don't worry, since you did not get a one-way bearing you do not need the ring to install it.  Installation is going to be a freeze then.

Hey Xarlio the one-way bearing is kinda expensive.  Be sure the one you buy comes with a tapered or conical ring to let you install the new bearing; it is really difficult to do it without this ring....take a look a the photo.