ICE warm, constantly running

I live in Los Angeles. I drive a 2014 Prius C I bought used almost a year ago from a rental company. Mileage now is 50k

My ICE is very warm- you can feel the heat on the hood a couple hours after I stopped driving. While I'm driving the ICE is on most of the time. In the Energy screen the orange ICE path is going both to the wheels and the electric motor most times it is on.

Starting yesterday I noticed a drop in MPG. About 10-15 miles. Usually the car starts at 99 mpg in electric mode, then fades down to high 40s when ICE kicks in. As of yesterday it has been starting at very low mpgs (less than 10) and climbing up as I drive, but in short distances no more than 42mpg. Instead of starting on electric motor the car now starts on ICE.

Today I had to drive a greater distance for a meeting. The Energy display showed the ICE almost continually sending energy to the Hybrid Battery- even when the battery was mostly full. Anytime the ICE was running it was also sending energy to the Hybrid Battery. There were a couple moments when the electric motor was running and still the ICE was sending to motor/battery.

When I got home the hood of the car was very warm where the ICE is. The inside of the hood was very warm as well with the heat coming from the ICE.

I have kept up with fluids and maintenance. Tire pressure is good.
I just installed a Kenwood KSC-SW11 powered subwoofer five days ago. The car had been running normally since then until yesterday when all this came up. After the problem came up I removed the power connections for the sub, but the car is still performing the same. I hope it is a coincidence.

Has anyone else experienced this?

 

Battery is measuring 12.8v. The only thermometer I have is for oral use. This was last night around 8pm that I held my hand on the exterior of the closed hood. felt the heat right up on the left side of the hood where the ICE is. Right side of the hood was cool. I drove 50 miles, stopped for 20 minutes, then drove another 12 miles when I felt how warm it was. Opened hood and felt hot air all around ICE- can't estimate temperature but it was enough to share heat with the stand bar. Yesterday was around 90 degrees during daytime. Yes had air conditioning on. Drove in slow traffic and a large portion of the 50 miles on the street. However, during that 50 mile trip I did get 50mpg.

This morning the car seemed to run fine- I tested it again late last night around midnight, filled it up and got 47mpg for that short trip. It still started at 0mpg at the start and the 'current mpg' was a slow climb up rather than a descent from 99.9 .

Today on the way back from work (around 93 degrees) the hybrid battery was halfway entire time. The Energy Monitor screen still showed orange going from engine to battery most of the time, but the battery indicator didn't increase or decrease that ride. Less than 10 miles.

Went out two hours after getting home and still only the ICE was warm. Not burning hot to hand, and to be honest I don't normally go up and touch to see how it feels after a drive. But it seemed warmer than what I would have expected for sitting there after a short drive.
I filled the coolant about two months ago. I just looked at the coolant and it is actually a bit above the fill line. I opened the radiator fill (cap with "do not open if hot" - that part wasn't hot). The coolant was still all the way up to the cap. Could it be a radiator issue?

I may just be extra cautious after installing the powered sub. First thought was maybe I didn't ground properly- I connected to a metal bolt by passenger seat. Verified 0 ohms from that bolt to the grounding bolt to battery terminal's connection to ground. I disconnected the sub from battery and ground last night, but after today it doesn't seem to be the cause of the issue.

Wondering if I should instead have my ground for powered sub going to the bolt that goes to the clamp which holds the 12v battery in place.

 

Heh... full story: I had two destinations, so the 20 minute stop wasn't just me waiting for my car to charge up if that's what you're getting at.The reason for my concern was the engine being hotter than any other car. High climate and new stereo installation had me thinking all over the place.

Anyways it looks to be the fan for the traction battery. In Energy Monitor it showed a brief instant of the ICE and hybrid battery going to the traction battery. They were both working to help cool down the traction. After removing the panel I saw the fan was completely caked with lint. I had vacuumed through the panel before thinking that was enough, but it seems the previous owner never did.