ICE not shutting off

Can be many reasons. This time of year (changing seasons with rapid temp. swings) a common reason is cabin heat requirements; also related, ICE takes longer to reach full operating temps/final stage. Colder temps=weaker battery=more ICE use.

 

This is one of my oldest Prius videos with an aftermarket gauge. It illustrates how engine on/off relates to speed and coolant temperature.

 

You have a 15 year old car.
If it still has the original HV hybrid battery, what you describe can sometimes be an early warning sign of battery failure.

 

Umm no, it is not a sign of anything. It is a perfectly normal situation – for a Gen 2.

It is actually 7 seconds. What you have described so precisely is the transition from warm-up stage 3b to stage 4 and is a perfectly normal transition from stage 3a/3b to stage 4 of the hybrid warm up. Pressing the brake pedal harder does not have any effect on the engine stopping any quicker. It is just happening coincidentally.

Read the link in my signature "Hybrid Warm-up: 5 modes of Prius Operation." for more detail of what is going on, if you are interested.

 

It IS 15 years old.
I stand by my original statement.

You are ASSuming that he is describing the situation accurately AND that you have a perfect understanding of that.
It is possible that neither of those things is true.

If you suddenly notice that the ICE is running longer or at times it didn't used to.......then calling that "normal" likely is a stretch.

 

Did you read my post ?
Do you have the original HV battery in it ??

 

It is more likely that it has happened before and you just haven't noticed it until you noticed it and now you notice it all the time. This is quite a well known psychological phenomenon. When I first noticed it I could have sworn it 'just started' doing it. But as I researched and got to know my generation Prius, I soon found out that it has been doing it all along and I just hadn't noticed it. My car has the original 14-year old HV battery too but I first 'noticed' the behavior over 10 years ago after having the car for 2 or so years, so yes in this case the HV battery's age is irrelevant.

Another thing is it tends to be more noticeable when you are doing trips of 15-20 min or longer, due to it being the transition from stage 3a/3b to stage 4. Shorter trip and it just doesn't come up as there isn't enough elapsed time for it to be ready to transition.

Another thing to be aware of is there is a difference in behavior between the transition from stage 3a to stage 4 and the transition from stage 3b to stage 4. In the latter scenario, the engine will behave as you observed, where the engine continues to run for 7 seconds to do its little calibration routine and then shut off. In the former scenario, you will notice the engine never shuts off when you are gliding (some call it coasting), or going down a decline (where the car is clearly regenerating and the engine should be shut off) but when you come to a stop, the engine has already shut off or shuts off immediately. In this case, you can force the car to go to stage 4. If you hold the car firmly with the brake pedal and give the accelerator a quick burst to force the engine to start and then release it, the engine will stay on for the 7 seconds and then shut off. In both cases, the warm-up cycle is complete at stage 4.

This particular quirk is unique to the Gen 2 Prius, so Gen 3/4 Prius owner or Prius c owners will never experience this for themselves. There are probably former Gen 2 owners out there that might not have ever noticed it.

While it is perfectly true you have a car with a 15-year old battery, you can't just start there and make all sorts of assumptions, especially when you described the 3b -> 4 transition so precisely, in my mind there is little room for doubt. I would not be so bold as to say I have a perfect understanding of the warm-up cycle but I do have a very good understanding of it and I am very confident the information I am giving you is correct.

Be assured there is nothing wrong with your Gen 2 Prius despite what some other less informed contributors might be saying.

One last thing I found out accidentally from experience, is that you do not need to be at an actual full stop for the calibration to happen. It is only necessary to be traveling less than 3 km/h (or 1.8 MPH).

Enjoy your Gen 2 Prius, drive long and prosper.

 

How do you reprogram the throttle body?