No EV at startup?

how long after you press power does the engine come on? does it come on if you just sit, or only if you start driving?

 

I think this might your culprit. It probably needed the ICE to generate enough heat to meet your demand for a 20º temperature boost. I can't say for sure since those temperatures are exceedingly rare down here, but I don't see anything else on your list doing that.

You can test the theory by turning off the climate control when you stop the car and see what happens when you start up w/o any heat. Heated seats and steering wheel won't start the ICE.

 

I experienced a similar thing on my 2021 PP two days in a row, but not exactly the same. Mine stared in EV mode but canceled by engine staring shortly after starting to drive. Yesterday morning, the temp was 26F and I had to start the defroster to get the heavy frost off from the windshield. It was a short trip to a local pharmacy about 10 miles. Since I had to start the engine for the defroster, I drove to the store on CHG mode. I had only ~10% SoC before starting the CHG mode. At the pharmacy, I ended up with ~30% SoC. On my return, the temp was well above 32F by then and I thought I could drive back on EV mode without the engine coming on. The car started in the EV mode but as soon as I started driving, the engine came on. After the warm-up cycle, it did get back to the EV mode. I thought this was due to the climate control setting too.

Then this morning, I had the car charged overnight to full 100% SoC. The temp was below freezing early morning and I had frost on the window, but as soon as the sun came out, it melted. so I did not have to use the defroster. For this morning, I did not use heat (HVAC was off, no steering wheel nor seat heater). The car started in the EV mode as it should, but after a few miles of driving, inexplicably the engine came on canceling the EV mode. No, I was not going downhill. It finished the warm-up cycle and returned to EV mode eventually. After ~16 miles of the drive to the destination, on my return trip, I had plenty of SoC left but the car did the same thing. That is the engine starting and canceling the EV mode shortly after starting to drive, despite no heat nor defroster being on.

I know the engine comes on PRIME for no obvious reasons sometimes, but I don't remember this happening to my previous 2017 PP. I don't have any proof but have a feeling that Toyota tweaked some software settings in 2021 that resulted in a longer EV range (most likely due to higher limit of charging threshold) and maybe raised the threshold temperature and/or maybe lowered the threshold load on the system for the engine to automatically turn on while in the EV mode.

More testings are needed to confirm this.

 

Sal, a couple things come to mind that might have an effect on the ICE starting up during a cold snap fairly early in the season.
were you able to precondition for either trip?
and have you done much switching mode EV-HV-EV etc. driving is the newer Prime?

A slower paced warmup while in EV mode might be something else to give a shot at.
I do both slow driving in EV and HV modes during initial startup, whenever I'm not in a flaming rush to make my destination. It can help with visuals of how efficient / not efficient the warmup cycle can be at the temp boundaries the car sees, if that is how the thing is programmed.
I've seen kinda major shifts every 20 F and some minor ones in between the 20 F like at 55 and 40 F.

 

Yeah, I have to drive in a cold morning a few more times. I just don't remember this ever happening on my 2017 PP at this temperature. The first time happened yesterday, I thought it was the heating that caused it. It was well above 32F when we started back from the pharmacy, but I was with my wife, so I had the heat (HVAC on Auto 70F) and had seat heaters on. But today, I was alone, and I had no heat (HVAC off, seat heater off, steering heater off).

No, preconditioning for either day. I never use preconditioning. For both days, the car was started in EV mode and had not switched to HV before the engine started on its own. And my driving style is almost always slow start and slow going in town. When the gas was cheap, I did quite a bit of switching HV/EV, but now the gas price is very high, if I have enough EV range left to complete the trip, I plan to use EV mode exclusively. But, comes middle of winter, if the temp dips below 30F, I will likely start the car in HV for heat. I almost never use the heat pump for heating.

 

Wow. It does seem like Toyota made some kind of change. I've driven in EV in temps down around 30 or a little below without the ICE coming on.

 

I just drove ~10miles in very similar conditions as the last two days. But the car did not start the engine this time.

The nighttime low was 26F. I had the battery charged last night, started around 10pm. So, after the charge was complete, the car sat ~5 hours. Heavy frost on the windshield in the morning, but was gone by the time I drove. The ambient temp was 39F then. The traction battery was full. Did not use HVAC or seat heater first. In the middle of the drive, I turned on the HVAC set to high fan manually, with or without AC, then set to AUTO 70F. Also, turned on the seat heater. None of these caused the engine to come on. I was able to complete the entire 10.3miles on EV mode.

No reproducibility may mean the last two days were just random occurrences of the engine coming on PRIME for no obvious reasons.

 

Seems strange. I drive a 2018 and very seldom has the engine kicked in when in EV mode... even at temperatures below freezing.

 

up here it's been about in the 20's when I leave for work and I haven't had the engine start until EV range is depleted or I ask it to by switching to HV or EV auto or turning on front defrost.

Are you slapping the EV button as soon as you turn the car on and switching it to HV? It starts in EV if it's been charged. Or lovingly holding the EV button in until charge is activated?

Are you sure you haven't hit the defrost button by mistake? my phone cord will trigger the the capacitive buttons on the side of the 11" screen if it brushes against them while I'm fumbling my phone into the vent magnet holder.

Are you selecting EV auto and then peeling out of your garage with the pedal to the floor?

Have you been driving on EV for so long that the gas is about to go bad and the computers are deciding now is a good time to burn it off? I believe there is some sort of maintenance mode that will burn some gas before it goes stale.

 

There is a bug where if you turn on the adaptive cruise control with greater than around 85-90% charge in cold weather it starts the engine. Also, at less than 90% charge cruise control seems to cause more random engine starts in cold weather. I don't know if non-adaptive cruise control does the same thing (hold the cruise control button for a few seconds to turn that on).

I recently had the engine come on at around 85% charge going down a fairly small hill, only using the brake pedal to slow down. Hybrid Assistant showed the battery temperature was around 42 degrees F. Using B mode makes the engine much more likely to start.

How recently the battery was charged seems to have an effect, even accounting for temperature. The more recently it was charged the less likely the engine is to start. If it was charged a few days ago, the Charge Current Limit and Discharge Current Limit are reduced, and if you call for braking or acceleration too close to those limits for too long the engine will start. I always set it to charge for departure at 6am unless I know I want to charge immediately.

If the battery temperature falls below freezing it is almost impossible to drive in EV mode because the CCL and DCL will be so low. For example on a warm day, DCL is usually around 68kW (91 horsepower), but I have seen it as low as 26kW (35hp) when the battery is cold. The car knows that is not enough to safely drive, so it starts the engine when you call for even a moderate amount of acceleration.

The battery has a lot of mass, so it cools off and heats up slowly. Leaving it unplugged one night in moderately cold weather (20's F) is usually not enough to get it below freezing if you drove it the previous day.

The seat heaters will never cause the engine to start. The power consumption is pretty minimal, maybe a few hundred watts.

If you have the heat on and the engine is already warm, it will periodically restart to stay warm.

I have driven to work in 10 degree F weather purely in EV mode. It is only possible with a freshly charged battery, heat off, seat heaters on, and maybe slightly open a window to keep frost from forming on the inside of the windows. I don't recommend it.

 

I have a 21 prime. I have an issue getting it to run in Ev mode with full charge. Sometimes it will start and run in EV No problem and sometimes it insists on running ICE. Dash shows I am on Eco and EV but engine is running andsuppling the power. It take multiple try’s cycling thru drive modes and pressing EV selector to actually finally get it to run EV. Am I doing something wrong at start up to cause this issue

 

Maybe read this thread that is recent and on going.
Could help

No EV at startup? | PriusChat

 

I doubt a dealer would be any help on this. They are mostly clueless about how the EV/HV works on PP, to begin with. There was another post by a different 2021PP owner asking about the same thing, That is, how to keep the PP in EV mode.

Getting prime Toruń in EV mode | PriusChat

Yeah, I still think Toyota tweaked something on 2021 compared to 2017 PP. I also owned a 2020 PP, but I really can't say much about the normal behavior of that car for I only drove a few times on a full charge and I was always switching EV/HV when I was driving. I Will report, if the 2021 PP starts the engine again inexplicably in the future.

 

OK, this is the second post on this topic, and at least third person (including me) seeing this behavior, that is PP not able to run on EV mode despite the fact SoC is there. Yeah, let's consolidate the thread...

 

This may be a silly comment, but do you have the front windshield defroster on? That A/C setting will cause the ICE to run and, once started, the ICE will continue to run until the catalytic converter is warmed up -- even if you turn the front windshield defroster off.

 

I am not driving daily now, so I don't have as many opportunities to test different parameters, but after two incidents I mentioned above comment #4, two subsequent drives went fine with 100% EV mode without the engine starting. Like you, I can not pinpoint the cause of the engine starting. It seems it is not purely dependent on the temperature or SoC level.

BTW, as you probably know already, once the engine starts it must complete the warm-up cycle before it shuts down. The colder the ambient temperature, the longer it takes to complete this warm-up cycle. In wintertime, mine usually takes ~5min whereas in summer this can be as short as a minute or two.

 

Yes, I know the feeling. But when it's happened to me, it's usually been because I was reaching toward the big touch screen on my 2017 Advanced and just brushed against the front defroster "button" which is not a mechanical button but just a touch switch. This appears to start the internal combustion engine regardless of the ambient temperature -- for example, to defog the windshield on a humid summer day. I think it's intended to produce a lot of heat quickly because Toyota reasoned that windshield visibility is a critical function.

And, even if I immediately realize my error and touch the "button" to turn of the front defroster, the engine will continue to run until it has warmed up (catalytic converter / air pollution) before automatically shutting down. If you want to stop it sooner, you must completely stop the car, turn the car off completely, and re-starting.

Please note that the rear defroster is an electric heating element in the rear windshield and that whether it's on or off has no effect on the engine.

It sounds like this probably is not your issue.