I was gifted a 06 Nissan frontier. Engine and trans have already been swapped. 258k on body. Was told over 100k less on engine and trans. 4.0, automatic. 

Anyways I was driving it all over just fine. Went and got the tags up to date and all.

And had a guy look at it for me. He said the radiator caps weren't on right. I guess one cap is pressurized other isnt. So he swapped em, put one from reservoir onto rad vice versa. 

And idk if this is what caused the issue or not. But since, I will be driving and I stop, and the reservoir is bubbling and steaming. Im like wtf. And my temp gage is still under half.

I dont see anything milky on dipstick or oil cap. 

I read online that the caps were on the right way, dude switched them the wrong way. Put the non pressurized cap on the reservoir. 

Really hoping this didnt mess anything up. I was so excited for this truck. Its also worth several grand well it was anyways. 

I think he thought something was wrong because the top rad hose was hot and bottom one wasnt nearly as hot. So I changed thermostat, and top hose would still be hot, and bottom one wouldn't be nearly as hot at all.

So I was advised to remove the thermostat. Since it doesnt snow where I live, nor get to freezing or anywhere close to freezing temps. It wouldn't matter was told 

So I removed it. And now both top and bottom hoses are the same temps. 

And even after putting the rad caps back in right spots, taking thermo out. The reservoir is still bubbling after driving for a few mins. And temp gage stays under half. But my scanner was reading it was going up to like 102c when driving but wouldn't go higher.

Also

So I saw theres a electric fan behind clutch fan, and im like hmm why isnt it coming on, and I saw the connector for the ac pressure thing was broken, or half broken. And im like hmm well I do remember hearing the electric fan coming on and off before. So this must of recently happened.

So I tried to jump the electric fan, by connecting the 2 of 3 wires to the batt from the ac pressure switch connector, I cut the connector off. Put the black and red/pinkish wire to batt and nothing happened. 

So friend told me try jump relay, so found the high speed fan relay, I jumped two pins and fan came on, was like OK great. Then I touched two wrong pins a couple times. And didnt really notice anything happen.

Well I was all excited ok, I just need to jump this fan, maybe wire a switch and everything will be fine. So I jump in truck to go to orileys get some supplies, only down the road.

And I have little to no power at all. Car barely moving.

Codes im getting are p2122, p2138, p0643

Tried unplugging and plugging back in tps sensor, tried clearing codes several times. Checked the fuses. Nothing worked. Still low power.

Im wondering if touching the wrong two pins a couple times on the cooling fan relay messed up the fuse box or the wiring harness itself. 

Or maybe somehow the tps sensor got messed up. Which is $300 new at orileys. Trying to find a used one right now. 

Or maybe trying to jump the fan from the ac pressure switch connector, messed something up?

Im heartbroken my new truck is messed up now. I was about to sell my old 90s car and keep this nice frontier. 

Please help,  thank you