Required minimum coolant temperature

Hard to answer. It's not just engine temp that governs engine shut-off during warm-up. Some other factors:

1. Temp set on the Heat/Vent system. With partially warmed engine, if you roll to a stop and engine continues to run, try ticking the temp down a degree or three; often engine will shut off. Or turn H/V right off might be needed to do the trick.

2. Mode set on the Heat/Vent system. Heat/Defog mode in particular will tend to keep the engine running.

3. Outside air temp. Well this one I suspect, but it seems to be: if it's bitter cold, it seems to take that into consideration, delays engine shut-down till higher coolant temp is reached.

4. Goes without saying, but: Hybrid Battery state of charge down to two bars.

 

Some info I copied back when I had my 2010 IV...

 

If the heating is deactivated, the engine switches off at 40°C / 104°F.

Posted via the PriusChat mobile app.

 

Not yet mentioned is the need to heat up the catalytic converter so engine exhaust burns cleaner... And partially mentioned is how much charge the hybrid battery has, as engine will idle longer before shut off if charge is low.

 

I can reliably get EV mode at start-up, IF I plug in the block heater for at least an hour. good for maneuvering the car out of the garage to the driveway or street, stuff like that. It kicks me out if I exceed ~15 km/hr.

 

That is what I see, at least while in ECO mode.

My engine coolant temperature needs to be above 68F / 20C to get EV mode.

Curiously, I've never ever seen the OBDII-port / ScanGauge display 68F. Always 67 or 69F instead, over very many observations. And once managed to watch it transition from 69 to 67, cancelling EV and starting the ICE.

 

Wow, I wanna do that... Does it work on Gen2 as well as Gen3?

Do you have a link on here to describe the block heater you used, as well as install advice? This is exciting! What's temp the block gets coolant up to?

 

Monitoring coolant temperature continuously with my ScanGage 2, the ICE usually cuts off in the 120-130 degrees F, range.

 

I haven't been bothering with my ScanGauge for a while. For one reason, because it was starting to trigger "Check Hybrid System" warnings.

Anyway, I found an hour with the stock Toyota block heater plugged in was enough, on the coast just up the road from you. Maybe a little more if it's near freezing. You've got about 15 seconds after start up, to try for EV, and see if you get it. If not, shut down quickly and let the block heater go another 1/2 hour. But an hour always seems to do it for me.

As @fuzzy1 notes, it "might" be on the cusp, will give you EV, but then coolant temp drop a degree or two and it decides to kick in the engine. So far it's worked well for me though.

It's a little odd, but it seems like US dealerships don't usually have the block heater. Not sure why, because it can a LOT colder in north/central States than out here on the coast. Anyway, this is the part number, when I replaced ours, in Oct 2019:

PU140-00905

It was $90 CDN, they had to order it in; took a few days.

I installed it myself this time. On third gen it was a royal pain. A factory install before the engine is dropped in would straightforward, but the bear is all the cables/conduits/brackets in the effing way if you do it after the fact. It's a heater bar that goes into a socket on the drivers side rear corner, round back of the engine. There's a thermal transfer lube you apply to it.

I would dry fit it first, and that means unbolting brackets, and pulling/tying stuff out of the way as much as possible. I also raised the car and took off the undershield (2010), and did the final insert reaching up from below. You can't see what you're doing. Put it in dry, then just back it out, get the grease up there, baste it up, and back in. There's a tang that snaps into a pocket to lock it in place. And for sure have the power cord pushed into the heater element first.

Here's the Toyota Instruction for third gen, but it doesn't really address the difficulty of access (part no superceded). I didn't take the wipers/cowl off, but it mighta helped:

 

Confirming what @hoffeck said.

I am watching the temps all the time now since my old engine was blown and I have a fresh rebuild.

104F is the temp the engine will shut down without the heater being used.

http://www.RedBullet.net

https://ProjectLithium.com/?ref=mG0GE

http://www.Pulstar.com

http://www.PlugOutPower.com
Use code 7373

http://www.hybridpit.com
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http://CatStrap.net
Use code azusa