New Traction Battery, Engine Running, MFD Not Displaying, Low MPG

Hi all,

2 weeks ago, I had a new OEM Toyota Hybrid Battery installed in my '08. Afterwards, I flushed the pistons with B-12 solvent (according to some threads here), changed oil, installed new spark plugs, and cleaned the MAF.

Immediately after performing the flush, the Red Triangle flashed on + check-engine light. After driving around and parking, the Red Triangle went away, but still check engine: P3190, which I cleared.

Now , the car fluctuates between two states. Normal state, which is great. Low MPG state: the ICE motor runs a lot, MPG seems lower than usual, and the ICE motor even runs when the MFD says it's not running.

As in, with only Blue Recharging arrows to the Traction battery, the ICE motor is still audibly running and my MPG reflects that.

Anywhere from ~5 MPG to ~80 MPG with the ICE motor still on, but the MFD says "recharging" (usually 99.9 MPG). When the car correctly shows the ICE motor on, I get low MPG. Average around 35.

Sometimes the car switches to normal mode, and drives great and normally.

I'm confounded, but happy to be here. What can I do?

 

Some important context: The weather is cool, but not that cold. 44 F low and 54 high. I've read some other forums that the car might likely be trying to warm up. However, I'd expect the car to be warm after 15 minutes or so of driving and thus not exhibit the low MPG behavior- which it seems to do.