Oil Pressure Light

The engine doesn't need oil pressure when its not turning. When it IS turning, it has pressure. When the ICE starts up, it is first spun up to 1000 rpm before fuel or spark is applied, thus providing lubrication.

 

Aside from pissing off all the drivers of hybrids, what would be the point to having the oil pressure light come on when the engine is off?

What good would it serve? How would that be a familiar behavior? (Our alternator light should be on ALL the time as Toyota did not install an alternator!)

 

The answer is pretty simple.
That is that our Prius is smarter than we are.

The Prius knows what the proper oil pressure should be at all times. If the ICE is at 0 rpm then 0 psi is the proper oil pressure and so... no light.

Realize that the oil light in all modern cars is controlled by the computer. The day of having a light connected directly to a pressure sensor is gone.

Thanks,
Dan

 

Perhaps the simple way of answering this question is that in a normal car when you turn the engine off the oil light does not come on. This is because you also turn off the supply to the warning light.
Now when you make the Prius "ready" you are not turning the engine on, you are only turning on the computers. It is these computers that turn the engine on, or decide if the the engine needs turning on or not also controlling the warning lights associated with the engine.

John (Britprius)

 

Yes, it is traditional on all cars to do a lamp test during power up, so drivers expect it.

So far, it only seems to be confusing you. The rest of us expect that when there is no issue, we won't get warning lights about that issue. Thus we do not need to panic because we got a "check engine' light when in EV, and we are saved from getting an alternator light on a car built without an alternator. We trust that when we get a warning light, it means something has gone wrong.

I am going to jump out on a limb here and guess that just because everything else on this car is controlled by software, that the computers know not to give false warning lights as well.

 

I understand why you asked the question, but it is not speculation regarding the the control of the light being the computer. That is fact.
The driver has limited say or input as to if the engine is running or not, and "ignition on" the normal control of the oil warning light is part of the sequence controlled by that computer.

John (Britprius)

 

sometimes, the question is more elusive than the answer.

 

No.

 

This is on the hatchback, but I'd assume the v is similar:

If you're stopped at a red light, the mpg indicator is going to tell you you're doing infinitely good mileage. Even if the engine comes on, it'll continue saying this.

Nothing could be further from the truth, but in that situation the gauge is irrelevant, so it's just shut down.

 

The v displays that, ICE on or not, MPG at rest is zero.

 

To simplify, when the Hybrid computer switches the engine (ICE) off, it switches the 12v feed to the oil pressure light off, equivalent to switching the engine off on a non-hybrid.

 

then where does the pressure come from when the ice is off?

 

Who's on second?

 

What makes you think there is any pressure when the ICE is off?

The computers simply don't send an electrical signal to the low pressure lamp

 

When the ICE is running as a pump/brake, it must have lubrication, even if combustion is not called for.