Warning Light under 1/4 tank of gas

I understand this topic has been almost beat to death but I had a hard time finding specific points to this situation.

2003 Prius
216,xxx and climbing as it is my daily

Girlfriend owned it for 4-5 years and it would occasionally give the exclamation/warning light/check engine light rarely. It was only when she was low on fuel though. I only recently learned of this.

I now drive it daily and absolutely love the thing.

Once 2 bars or under are left and I go to start it, P3191 is recorded, engine will not start. Once I refill it, engine starts up with no issue. After 2 or 3 key cycles, all lights go away and it's a normal car again.

Short term fix - Do not let fuel go under 1/4 tank. This is a good practice anyways.

Long term fix - Fuel tank/pump replacement? Looking for outside thoughts and advice.. Thanks in advance.

 

No one has any good information on this?

 

Update:

1/27/17– Fuel level at 2/3 to 3/4 - Serviced the transmission with a fluid change and pan cleaning after the car sat for a couple of days. I drove it roughly 30 miles and drove normal. Parked the vehicle for 10 - 15 minutes. Upon restarting it, MG1 attempted to start the engine but the engine would not fully start. After cranking the engine for 4-5 seconds, the engine began to shake and stumble as if it was attempting to start up but was lacking something, then eventually died so I shut the key off and proceeded to wait. The check engine light, exclamation point, and problem/warning light on LCD screen all displayed at this point. This same symptom happened 3-4 more times each time I attempted to restart the engine, each time shaking and stumbling. After waiting 10 minutes, I restarted the vehicle again, all warning lights were still on but the engine was running smoothly. I drove a mile or two till I got home with no troubles. Once I got home, I cycled the key 3-4 times and the warning lights eventually went away. My girlfriend reported this problem to me roughly 4 or 5 times over the past couple of years. The difference is when it happened to her, the fuel level was always low (1 bar left).

I have only owned the vehicle for the past 2k miles, but I've been around it for the past 2 years.
I recently replaced spark plugs, air filter, oil (synthetic), transmission ATF, cleaned MAF sensor with MAF cleaner, and checked compression right when I got it around December 1st, 2016 with 214k miles. Since MG1 wouldn't allow me to roll the engine over at 200 RPM like a proper compression test would like, I was forced to do it using MG1 at full power. Compression came back well and equal across all cylinders.

No oil usage present.

I am not a very aggressive driver. Occasionally, I will pass someone on the highway and have to get after it a little bit. My normal driving habits are 50 miles each day, set the cruise at 63 and just ride along. I don't see a 1st gen Prius as a real "go getter" vehicle haha.

Health of the HV battery is something I cannot tell you. My MPG seems normal to my standards and I have had no issues with the hybrid system itself (that I am aware of).

I have maintained this vehicle lightly in the past few years but only recently have really hit it hard with service and replacement of worn parts. It has had regular oil changes over the past few years. I know that probably doesn't help a whole lot.

The throttle body has a little bit of light carbon inside of it. I can remove this and clean it if it is thought to help. I read another post that said cleaning the carbon from these doesn't really help if they are sticking. I will clean it anyhow.


I plan on doing a Fuel pressure test and battery load test when I get to my shop tomorrow morning. The issue is intermittent so I am reluctant to think I'll find any obvious problem unless the car is having its hissy fit again. My best hope is to run the vehicle low on fuel again near my shop and hope I can do tests after the problem is current. I'm not sure this will actually happen, but it's an idea.

I will look though the TSB to see if there's anything there.

In the meantime, any further bits of information would be great! Thank you!