Monitoring Engine Temps

Your picture didn't come through but an OBDII monitor isn't necessarily a bad idea.

You said your kids were taking the trip:

Are they going to pay attention to the OBDII monitor?
How many miles on the 2011?
New or used?
(I presume 'used' since your signature indicates you're still rolling a G2)
Does it use oil between oil changes?
Do you pay attention to your fuel efficiency?

The only temperature issues I've seen with Priuses come from failed water pumps, failure to bleed the coolant loop following a fluid change or a coolant loss from a famously all-too-frequent head gasket failures.

How many weeks before the trip?
Major maintenance is generally not advisable before a long road trip BUT you may have time to sneak in an EGR clean.

Good Luck!

 

I have used a P10 obd2 connected device for over 5 years to monitor temperature.



The cost is low and it has configurable alarm limits which means you don't have to watch it. I set engine temp at 210f which is considerably lower than the vehicles 248f light which sometimes is ignored.

The P10 configuration pdf is not entirely clear but I have not experienced CAN bus interference as reported by some Scanguage users in the past. I also don't see increased parasitic draw when the car shuts down after the P10's configurable 3 minute delay to sleep mode.

A major failure such as a leak is rare but some report under performing water pump circulation without water pump specific warnings. I have never experienced a water pump failure but found that occasional observation of engine temps allows you to understand normal temps. I sometimes see 205f during high rpm grade climbing which quickly returns to 195f in normal low or high speed driving.

Ambients of 110f is not an issue although I have seen inverter temps rise in stalled traffic, with high ambients and ac on high. However no negative results.

There are frequent reports of head gasket leaks causing low coolant levels over a period of time. Checking the coolant level periodically is important and is something I would do daily on a trip. Often the vehicle's overheat warning at 248f will flash and go away, likely caused by air/combustion gasses in the coolant.

I normally would not drive my gen3 further than three hours away because of the risk of ending up at a dealer in a costly failure situation.

If I were sending my kids cross country and it was not a move, I would find another car or rent something.

 

FWIW,:

I had a ScanGauge hooked up to the OBD port constantly, for a few years, and then started getting "CHECK HYBRID SYSTEM" warning, coupled with brake and skid-control lights on dash, plus "work to rule" brakes. Basically felt like no brakes at first, the realized they were "working", but required more effort, seemed clunky. This happened at least three times.

Dealership mechanic suggested to disconnect the ScanGauge for a while, as a test, which I did, and problem never arose again.

Going on a road trip might not be a good time to throw any curves at the car.

 

Yep... OBD2 port is not a reliable control port/data port for continuous use. It's just a legally required diagnostic port to use when car is having a problem. The most I use it continuously is on road trips for a few hours at a time during mountain climbing to monitor RPM.

I think the best solution for OP would be to hard wire in / or set up a wirless sensor as an aftermarket engine temp gauge. Something like this would work well: Digital Engine Temp Gauge Dual Temperature Record,Backlight User Shutdown | eBay

 

Insurance companies and corporations routinely wire in full time obd2 monitors without issue. Like anything, quality and experience matters.

With that said, I expect some vehicles are less robust than others and some aftermarket devices are more problematic than others.

 

^ +1 for post #4.

I installed a P10 display three years ago based on rjparker's recommendation. It is very easy to install and a small learning curve setting up the preferred display and the parameters that you want to monitor. You also want to change the alarm set points. I like it very much for monitoring the engine coolant temperature and the 12v system/battery.

I installed an Android Auto screen and reverse camera 4 weeks ago right next to the P10 display.

Edit: Here is a poor picture of my setup.

 

I've had a ScanGauge II connected in two Prii for a total of fifteen years now with never any interference issue. I think Mendel's may be the only report of such an issue that I've seen.

I have my ScanGauge connected via a right-angle cable connector and with the cable run up above the lower dash panel so there are smaller forces acting on the connector than if it were a long one sticking straight out.

The one interference problem I have had was with a home-built accessory that I had used a very cheap J1962 connector with unplated pins. My thing worked great for a few years, then started setting off a festival of warnings lights right away on being plugged in. Rebuilding it with a J1962 connector that had gold-plated pins solved that problem completely.

 

Do you have more information or a link about how to set something like this up? I tried searching based on the information in your post here and wasn't able to find it.

 

Where can you buy those?

 

The P10 displa,y can be purchased on Amazon, eBay, Aliexpress, etc. You install one end of the supplied cable to the OBD2 port and the other end to the backside of the display. Here is one listed on Amazon, P10 display

 

Attached is the config pdf for the current P10 Pro model.