I've been getting reduced engine power and stabilitrak disabled warnings, engine light, and yes its certainly running in a reduced engine power state. I had read somewhere this is also called limp mode and does this is the transmission is involved somehow but I'm open and skeptical to assuming anything yet.

P0697 Sensor Reference Voltage C Circuit Open. Did take it in the shop and the Brak pedal sensor was replaced, they tested it out and seemed to have fixed it. I drove home and from there agreed but next time driving later that day it all happened again and so taking it back again.

For the most part sharing the experience and symptoms to help others incase someone else experiences this.

How many miles on it?

How many miles have you owned it?

How old is the battery?

Are there any other codes?

111k. I bought in 2017, at the time 4 years old with 43k. Battery is 1.5yrs old, I do live in FL and so understand the heat shortens battery life. That code was in there twice when I checked but also I only have a cheap $30-40 dollar reader with limited ability to read and erase. :-\ I have considered getting something better, I'm not sure if a higher end reader can give more info around codes or they come with other features like key programming and such.

You can get a much better tool for less than a diagnostic charge at the dealer.

P0697 Code - Sensor Reference Voltage 'C' Circuit, possibly something going wrong with your PCM.

A PCM is generally too expensive to diagnose improperly, so I suggest you try this first:

1. Check for good connections on the battery terminals.
2. Check all ground points
3. Check charge voltage at idle from the jump-start locations in the engine bay. These are not the battery because the battery is under the second row passenger floor
4. Connecting a real volt meter to the jump-start locations in the engine bay. Watch what it says as much as possible with the hope of catching a transient volt-drop event right before it sets this code again.

At this point if nothing is found, it looks more likely that this is a PCM going bad, the easiest way to address this would be to take it to a mechanic, tell them the issue and what you've done to attempt to diagnose it, then let them diagnose it.

P0697 5V reference circuit 3 provides 5V to the MAP sensor(terminal 1 gray wire at the sensor) and to the APP sensor 2 (terminal C tan wire at the sensor connector). spec is 4.8 - 5.2 volts. If over or below verify circuits. If ok possible ecm. If with in spec component issue. Have seen issues with the APP sensor (gas pedal). Hope this helps.

Great point. great point...

Thank you for this advise, I did take the connectors off of the battery (in the 2nd row, yes) and use CRC contact cleaner - no rust or issues observed but still cleaned, I also did this for the connections to the PCM, and also the Gas Pedal position sensor (a guess based on something I read, gave me the idea). I did not think about the battery, checking the voltage at idle, or checking ground points (Watching videos on how to that properly now); would be great to do it anyway for assurance to eliminate it as a possibility. It is with the Mechanic now. First time he had replaced the brake pedal position sensor and it tested out okay for them after that and also myself on the trip home, next time driving it came back and so I took it right back. Further reading on symptoms of faulty PCM'* I would think this would be the case, I don't want to jump to conclusions but I have noticed some delays in shifting lately and I had in mind that I needed to change the transmissions fluid also once I get it back. I read the PCM controls the engine and transmission and so to me that'* further evidence pointing towards the PCM.

That code tells you the check sum of the module is having problems. Replacement is necessary.

Mechanic ordered a Throttle body today, after replacing the Accelerator Position Sensor and that not being the issue it seems like they did start probing and testing voltage. He told me they observed the voltage fluctuating between 4 and 4.9v. I said that'* probably it because the spec is 4.8 - 5.2. He was surprised I said tat and probably thought I was full of **** but we have a good relationship and joke around a lot. He'* knows i have a genuine interest and I told him credit goes to a member in the forum I'm in -> dpieroni3 We'll see... tomorrow part comes in.