No Start Due to Low Oil?

The engine oil being low would not have caused your no-start problem. I predict that you will need to buy a new 12V battery in the next couple of weeks, if you intend to wait for another failure before taking action.

 

That method of testing 12v batteries is not necessarily relevant to the Prius, and in any case the Prius does not have an "alternator". Here is how to do it:
Entering Maintenance Mode (aka 12V Battery Check) without Switching Headlights ON/OFF | PriusChat

Report back the numbers you get. I agree that the battery is likely on its way out. There are also many threads about increased oil consumption in high mileage Prii, so do keep an eye on it.

 

how many miles on her? is it the original battery?

i would be more concerned about where your oil went, than the fact that the car wouldn't start. how often do you check it, if at all?

 

Not an expert, but that does sound very strange. The car probably wouldn't notice being a quart low on oil. Just as long as the oil pickup is submerged. It still sounds like something electrical.

Is the 12v battery original? Depending on how it was tested, and how soon after being in the running car, it may have been a false positive. The original 12v battery usually only lasts a handful of years. Also, the Prius doesn't have an alternator, making me suspect the test procedure a little more.

On any other car, I might suspect the battery connections but the 12v connections on the Prius stay so clean that they usually make good connection.

It can be difficult to go to the store and get a 12v battery for the Prius. It's a fairly unconventional size and it has a vent tube fitting and unusual contact posts. Shopping for a Prius aux battery is usually better done online, if you're not getting another OEM battery from a Toyota parts dept.

Here's a diagnostic procedure for the 12v battery:

Toyota Prius: How to Check the 12v Auxiliary Battery Health - PriusDIY.com

There are several options for replacements, and the installation can be performed yourself if you're a DIYer.

***edit...there may actually be a shut-off feature linked to a low oil level sensor. Read about it here:

prius oil out then engine automatically shuts off? - Car Talk

If a low-oil sensor was causing the no-start, one wouldn't expect it to act like a low battery (dim lights, no locks, etc) and be resolvable with a jump-start, I don't imagine.

 

I can't seem to find a DTC in the Engine Control Module listing that relates to low oil pressure, which is strange. There is a condition that people report, where they are already dangerously low on oil, which shows the word "Problem" on the MFD typically when going around a corner or accelerating sharply, and also the oil can icon appears on the combination meter. So far, that I've seen here, no one has reported a clear case of the engine not starting due to low oil. That may be because the above "Problem" only indicates while in motion, whereas there is enough oil to fill the sump when stationary, so it gets noticed before the no start condition exists.

In any case, the bottom line is check your oil, just like every other car on the road.

 

I'm wondering just how close to one quart "about" a quart" is, and how close to full it was topped off to. If the oil was topped off to the full mark on the dipstick with anything close to one quart then it definitely wouldn't have caused an issue. In fact the car wouldn't have even known the difference (no sensors would detect it).

I find it strange that the dealer should recommend checking the oil for those symptoms, but in the end it's probably good that you did.

Anyway, it's most likely that something was inadvertently left on to drain the battery and that after driving it had recharged enough to pass the test. Either that or the battery really is bad and only passed due to a surface charge from just being driven.

Run the self test for the battery shown here: Weird stuff happening? MPGs dropping? Test The Battery | PriusChat

 

Correct. If you think about it, the Prius engine experiences low oil pressure many times in daily operation, every time the engine turns off when at a stop or when only MG2 is powering the vehicle. So the DTC would have to trigger only when the oil pressure switch shows no pressure, and the engine is supposed to be running.

Rather than have that happen, Toyota has an oil pressure icon appear on the MFD, upper left corner. However the driver has to be looking at the MFD to see that warning.

 

I would think that, since the admittedly variable oil pressure logic exists to the extent that it can put that "problem" indication on the screen, and light the oil icon, there ought to be a corresponding DTC set as well. At the minimum the check engine light should go on, and stay on. That would have saved a few engines, by the reports here.

To the OP, the engine has no oil level sensor, just pressure. All engines have to start with no pressure initially, in order to detect the low pressure subsequently.

 

the battery is date coded, but you have to remove all the stuff on top of it to find the code.

 

I have a 2008 Prius. Started having problems with the battery maintaining a charge overnight (would show 2-3 bars but increase as I drove around neighborhood— also red triangle and vsc lights on )— then no problem for rest of the day and triangle etc would go away. . Brought it in and codes did not show a problem with big battery. I replaced the 12 volt, spark plugs. Continued having same issue for about 2 weeks never having a decent charge in the morning, triangle and other dash lights staying on until battery charged up. Finally the car died while trying to do this and had it towed to garage. I ended up replacing bigbattery with refurbished battery ( with warranty) from a company called Hybrid 911. Car was fine with normal charge for a week. I drove 4 hours to Orlando and
The next morning ( yesterday) same thing happening. Subnormal charge and lights coming on. Got Advanced Auto to check codes. “ both tires front ABS system codes popping up. I called the 911 Hybrid customer service and the first question he asked was “is there oil in the car?” I checked and the oil was waaaaay low so I added 1.5 quarts. So far battery has been fine, no lights on this morning— left it for 8 hours at work and everything still fine with battery in the blue at 3/4 level. I’m not sure why the oil was so low as I change it every 3000 miles or if my problem is solved but I’ve had 6 weeks and $2000 worth of headache and I’m hopeful. Anyone have any input? I’ve stumped three different mechanics with this...

 

coincidence, prius are quirky