Seeking Prius DTC Code Wisdom

Good Day! I've recently purchased a very used 2014 prius. It has 147K miles on it, but more dents and scratches than my 2002 Prius with 370K miles that I just got rid of. (My other car is an 07 Prius with 301K miles).

I have a few issues with the my new used Prius. I enjoy learning and troubleshooting things myself rather than paying overblown prices for someone else to play "guess and check". When I purchased the car, it was made clear that the temperature control was not working. I have checked the fuses and they all appear to be good.

I created an account with toyota and found he service history of the car. They noted that a previous owner reported the issue and their recommendation was to replace the Air Conditioner Control Assembly. The owner declined at that time. I purchased one from ebay and replaced it, but it still has no life. When I press the "temp" buttons on my steering wheel, my dash display says "temp", but there are no readings. If I press any buttons on my temp control unit, they don't do anything. I cannot adjust the temp and the blower never attempts to turn on. The little green lights on the buttons never light up and the display on the module does nothing. HOWEVER, the words on the module are lit along with everything else when the car senses it is dark out, so that would indicate that some power is reaching the control assembly.

Additionally, I have a check engine light with the following codes present:
P0102 - Mass or Volume Air Flow Circuit Low Input
P0031 - Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)
P0141 - Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
P0403 - Exhaust Gas Recirculation Control Circuit
P101D - A/F Sensor Heater Circuit Performance Bank 1 Sensor 1 Stuck ON

How likely is it that these are all unrelated issues that need addressed? Or is it likely that the problem is a computer module or wiring? I'm scouring the google, these forums, and all the documentation I can find. I may end up paying a dealership to fix the issue, but even if I do, I want to walk in knowing what needs done. If possible, I'd prefer to do it myself and learn more about my Prius as I go.

Anyway, thanks for all the help that you guys give on this forum. I've used it for years to research issues with my older ones.

 

I've been looking at the videos to clean the EGR. I'm thinking that's where I need to start as far as the codes go.... But the temperature control unit is a major concern. It's much more than I thought it would be when I purchased the car. I had not thought about the importance of the defrost / defog. We've hit a few cold days here lately and driving the car is risky without it.... So, any tips on that in particular would be much appreciated!

 

Thanks for responding!

Resting Voltage: 12.69

History: I just purchased it 3-25-19, and the person I purchased it from did not know the history. It has not been taken care of very well and has a lot of dents and scratches on the driver's side and top of the car. I don't see any evidence of any major damage and there isn't any mention of it in the toyota service history.

Miles: It has about 148K miles on it. I've put a few hundred of those on it since I bought it last week.

Oil consumption: I haven't had enough time to know yet.

When I cycle through the display, my temp screen is blank. This is my primary concern as i think it may be why my temp control panel is not working. My theory (largely created in ignorance) is that it doesn't know what to do, since it's not able to tell if the car is hot or cold... I'm attaching a picture for clarification.

 

Sorry, I spent last night dismantling the HV battery of my 2007 prius.

I do have access to a multimeter and the wiring diagram. Hopefully I'll have time to dig into this tomorrow. Thanks for the advice. I'll let you know as soon as I complete the next step and have something to report.

Thanks