ICE comes on anyway

I've been analyzing the "Front Defrost" cycle:

• 0:00.00 - 3.6 mi, 199.9 MPG, 0 mph temp 32F (0C), SOC 80%, Engine OFF to ON, 0 gal
• 2:54.50 - 3.6 mi, 199.1 MPG, 0 mph, SOC 79%, Engine ON, 0.018 gal
• 6:02.25 - 3.6 mi, 107.3 MPG, 1 mph, SOC 78%, Engine ON, 0.036 gal
• 7:08.88 - 3.8 mi, 81.1 MPG, 15 mph, SOC 78%, Engine ON to OFF, 0.047 gal

Bob Wilson

 

I wouldn't program it that way. ICE is far more efficient when handling a load, so waiting top use it makes sense.

 

It just indicates temperature & load are not the only criteria. I suspect a variety of factors are at play, too many for us to unravel.

 

I'm still curious but then I've had it happen to me.

Bob Wilson

 

I've read, and reread the entire thread. It seems we still don't know exactly what is causing the OP's issue. I will now attempt to summarize what we've come up with so far, for the benefit of those who haven't read it all or don't remember it all.

The OP (priuscatprimeguy) has been having difficulty keeping his Prime in EV mode under certain circumstances which he and most of us would have thought the ICE should not come on.

It is clearly both speed and temperature related. The issue only occurred last winter when the outside temperature was below 40F, and then did not occur all summer, but has begun to happen again this fall as temperatures again dropped. If driven at speeds at or below 25mph, the ICE does not come on.

OP is driving in EV mode, using "D" (not "B"), with the heat off, defrost off.

This Prime is parked outside overnight. Issue occurs only at the beginning of the first drive of the day.

Battery traction heater is on.

Battery starts at full capacity.

OP has short commute, 2.7 miles.

ICE comes on at 35mph (no word on what happens if he maintains a lower speed above 25, say 30mph or 28mph). But if driven at 25mph for 1.5 to 2.0 miles first, then ICE stays off.

If charged immediately when plugged in, ICE does not come on the next day.

Issue occurs too frequently to be 200-mile "ICE maintenance" (which may be a myth anyway).

Hills were discussed, but deemed not a factor in this case, since terrain is relatively flat, and issue occurred both going uphill and downhill, as long as driven 35mph.

We have reviewed the list of conditions where the ICE can come on, even in EV, as documented in the manual. Unfortunately, one of the conditions is essentially, "whenever the car feels like it."

All attempts to reproduce by others have failed. Notably, nobody seems to have been able to duplicate ALL of the relevant conditions at once.

A defect in his Prime was suspected, but the OP drove a rental Prime for a few days and the rental did the same thing.

It was observed that the Prius ICE is so quiet that perhaps others were having this issue but unaware of it. The theory that PCPG had better hearing was quickly squashed when we learned that he was actually hard of hearing, from birth, an event which preceded his Prime purchase. Only then did we learn that he observes the ICE coming on using the Energy Monitor screen.

In the most recent test, ten minutes sitting in the car parked in READY before departure with climate at 65 ECO led to the ICE not coming on.

Bob Wilson is currently experimenting with front defrost settings.

My thoughts:

This appears to me to be a software bug or feature, and not a defect. The OP was able to reproduce the event using a rental car and a defect common enough to affect both would show up for a lot of other Primes so we would hear a lot of similar reports.

"The gasoline engine may also operate in circumstances other than those listed above." The system is obviously very complex, and although the manual can describe certain discrete situations where EV mode is overridden, I'm quite sure that the code is not written so simply. The exact set of variables that triggers this event could be extremely non-intuitive and appear "random" to us. Since our attempts to find an easy solution have so far failed, I am expecting it to be a combination of unlikely things.

There appears to be a hidden "warm-up" stage that only shows itself in rare circumstances. In warm weather, battery is already warm. In cold weather, if not triggered in the first 5 or 6 minutes, unexpected ICE operation does not occur and this stage is not noticed. We need to more precisely describe what happens in those first few minutes.

I look forward to seeing the upcoming videos.

 

Nice summary with a few comments:

I have observed this once about a week ago but have yet to reliably replicate the symptom. I agree that all of the prerequisite conditions remain unknown and hopefully the videos will give a clue.

One reason for my investigation of "Front Defrost" is once started, it appears to have its own logic about when to end. Static testing when parked showed it running way longer than expected. However, once I started driving around the block and turned off cabin heat, it soon stopped.

When we find a recipe to the symptom. We'll ask others to independently test and confirm the method. Then we can work to share the problem with Toyota ... an electro-political problem.

Bob Wilson

 

What about if it turns off once the coolant has reached a certain temperature, like 130F? (Check with a gauge.) I know that with my Prius c, the warm-up cycle ended when the coolant temperature was 104F. Obviously if a cold car sits running while parked, it will not heat up as quickly as if it was being used in drive, so the engine stays on longer.

 

Being Black Friday makes it easier if you need edit software. There are killer deals if hunt for them and have a bit of luck. I like using Pinnacle Studio.

With the dashcam footage, all I do is increase the contrast and decrease the brightness. That adjustment via software works surprisingly well. But if you do want to address lighting the old-school way, a simple piece of black felt can be quite effective. Just toss it over the camera area. With the heads-up display, that can be covered entirely without loss of any vital driving info.

 

I upgraded from 17 Ultimate to 21 Ultimate for just $24.99. It was some pop-up that appeared recently when starting up the application. So, I'm not sure what deals you'll be able to find. But with such good timing, there should be something compelling available.

 

With temperatures of 38-40F (3-4C) I tried again. No luck but I did get a chance to try my iPhone video and 'lessons learned.'

• make sure the iPhone is as close as possible to the object
• do testing at night to avoid sun and shadow effects
• time-lapse doesn't work well even with post processing

I manually tried "Front Defrost" again with an ON/OFF. The ON lights the green light but pressing the button as soon as the engine starts, the light goes out while the engine continues to run. But the time-lapse and poor video made measuring the run time impossible.

Bob Wilson