357: Prius Start-Stall... Or No-Start?

357: Prius Start-Stall... Or No-Start? Automotive Diagnostic Podcast · Jun 28, 2026

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Car

Toyota Prius

The Toyota Prius is a family hatchback that uses both a regular gasoline engine and an electric motor to help save fuel. It is a hybrid, meaning it automatically manages its two power sources to get the best possible gas mileage. The 2015 version is a highly practical, efficient car designed for everyday commuting.

Part

motor-generator

A special electric motor in hybrid cars that can either help drive the car or act as a generator to recharge the battery when you slow down.

Car

2015 Toyota Prius C

A small, highly fuel-efficient hybrid hatchback made by Toyota. It uses both a small gasoline engine and an electric motor to get incredible gas mileage, especially in stop-and-go city traffic.

Term

P3190

A computer error code in Toyota cars that means the engine isn't putting out enough power or torque.

Term

P0A0F

A computer error code in Toyota hybrids that simply means the gasoline engine failed to start up.

Concept

hybrid no-start

A situation in hybrid cars where the electric motor spins the gas engine so fast and smoothly that it sounds like the car is running, even though the gas engine hasn't actually started up on its own.

Part

EGR valve

A valve that feeds a little bit of spent exhaust gas back into the engine to help it run cleaner. If it gets stuck open, it can make the engine stall or not start at all.

LIVE

Welcome to the Automotive Diagnostic Podcast.

We're going to explore ways to sharpen our diagnostic skills, find learning resources,

and hear from experts in the automotive field.

This show is brought to you by Auto Rescue Tools and Isaac Rodel. If you've been looking for a

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I highly recommend it. Hey, what's going on Automotive World? Welcome to another episode of

the Automotive Diagnostic Podcast. My name is Sean Tipping. I will be your host once again for

this week's episode. Thank you so much for joining me. Today on the show, I've got another case

study for you. This was an interesting no start diagnostic on a 15 Toyota Prius. So if you work

on Toyota Hybrid stuff, particularly the Prius, but this can apply to other Toyota Hybrid stuff,

you may have run into a situation like this and you may be familiar with some of the things that

I'll explain in this episode. But if you don't regularly service these vehicles or you haven't

been down this road with the Toyota Hybrid stuff or the Prius stuff, it can be a bit tricky jumping

into it for the first time. And I can say I know a lot of people haven't because even though these

cars have been out there for a long time and a lot of shops are very proficient at diagnosing them

and repairing them, there are still a ton of technicians and shops that we deal with on a

regular basis that don't understand some of the differences that come into play when we have a

hybrid vehicle specifically of this brand versus just our traditional ICE internal combustion

engine with no high voltage battery, no electric motors involved with generating torque to move

the vehicle or charge the battery. And it creates some things that are a little bit different that

we need to understand and particularly in a no start situation. Obviously it goes well beyond

that as well. And we've talked a little bit about like isolation faults and things like that on the

show. But when it comes to a no start of the ICE, and you'll hear the internal combustion engine

referred to as the ICE quite often when we are talking about hybrid vehicles, and it's just

the easy acronym to refer to the gasoline portion of the powertrain versus the motor

generator, motor generators that are involved with supplying torque to move the vehicle. But

anyways, we still need the gasoline engine to start and run. Obviously we're going to use that for

power some of the time. But we're also going to use it to charge up the battery, depending on the

needs of the vehicle and the needs of the battery. Okay, so again, it's a hybrid, you got electric

and gas, it's pretty obvious that you need the gas to run some of the time. So when you have a no

start on one of these vehicles, there are some things that you want to consider. And number one,

if you're not familiar with them, like I mentioned, you're not familiar with the codes that are going

to set, you may not even realize that it's a no start. And that might be the biggest piece that

you take away from this episode if you don't work on these vehicles very often. But that's what

we're going to talk about here. And then I'll get to the conclusion on this one, which was somewhat

interesting to me anyways. But this is a 2015 Toyota Prius C. And it is a 1.5 liter engine connected

to the electric powertrain. And the actual complaint from the customer is that this would run for 15,

20 seconds, and then shut off. And then it would not allow you to even attempt to start it again

until you clear codes. Alright, now, this right there should be a big clue to you that there's

something going on where the engine runs for 15, 20 seconds, it sets a hybrid warning light on the

dash doesn't allow you to even attempt to crank it again, or to run it again, until you clear

codes out the scan tool. And the codes are going to be the big sign for you, the technician, so

that you can identify what's going on here. So the two codes that you want to pay attention for,

and there may be others, and there may be others to help you figure out why it's not starting. But

in this case, these were the only codes that I had. But they're the important ones to say,

oh, okay, this thing actually isn't starting. So there's a P3190 that sets in the engine control

module. And that just says poor engine power. And then there is a P0A0F, which sets in the hybrid

control unit that said engine failed to start. And there's a big one, right? Maybe I don't even

need to be talking about this on a podcast to this audience, because it literally tells you in the

code that will set every time that the engine failed to start. But that's the truth, the engine

did not start. Now, here's where technicians get hung up, or they're not as clear on what's going

on is that when you listen to the engine, you look at the RPM of the engine, it appears to be

running. And it appears to be running for that 15 to 20 seconds. However long, it's actually cranking.

Okay, so this is the actual electric motor spinning over the engine. And the engine is moving so

quickly at a cranking speed that you would think that it's running, it sounds like it's running.

But you get these codes after a period of time, because the computer has realized, oh, this thing

is not actually running. And if you look at the 3190, which is a poor engine performance code,

and that actually there is a 3191, which means that the engine does not start. I don't know why

that didn't set here, but it didn't. But the poor engine power code is that the actual engine torque

is less than 20% of the requested engine torque for six seconds or 100 crankshaft turns,

whichever happens first. What it's saying is, hey, I want torque out of the ice, but I am not

getting it after a period of time. And when it decides that's the case, it will stop attempting

to crank the engine. So it's not actually that the engine stalled, it's just that it gave up

attempting to start it. But if you're just looking at this at face value on one of these

hybrid vehicles, one of these Priuses, and it's attempting to start the engine, you would think

that it's actually running. And I've made that mistake myself. The first time I ran into one of

these on a Prius, it was a fuel pump. The fuel pump was out, there was zero fuel pressure,

and it wasn't starting because there was no fuel pressure. I thought it was running.

And so fuel pressure was not the first thing I went after because it sounds like it's actually

running. And again, that might be the biggest thing you take away from this episode if you

don't work on these cars, because you'll waste a lot of time. And here is the other thing. And this

is the big warning about not only identifying that, hey, this engine isn't started, but what can happen

if you attempt to start the engine over and over again. And actually, maybe before I get to that,

let me just give you a couple quick ways that you can identify this situation beyond the codes.

Maybe you just don't believe the codes. Okay, I want to actually verify that this engine is not

running, because it sure seems like it is. You can look at the data pins for the actual versus

requested torque, and you can see that the engine is not going to be putting out anything or maybe

very little, but most likely it's not going to be putting out any torque, even though some is being

requested. And it says in the code criteria for 3190 to look at these data pins, and you can assess

it from there. The other thing that you can do, very simple, be careful. But I think most people

have a good understanding of being under the hood of a gasoline engine is you can check the

temperature of the exhaust manifold. And in the case where an engine is not starting, your exhaust

manifold is going to be cold, you would be able to touch it. Now, don't touch it. If it's actually

running, because it's going to be very hot, but again, there's temp guns, and there's ways that

you can determine, is the manifold actually hot or not? And again, surprising if you've never run

into this, because you're like, it's running, clearly it's running, it's almost 1000 RPM,

that's the cranking speed of these Toyotas. So again, if you haven't run into that, that's new.

Now, if you continue to attempt to start it, and you have the clear codes every time, at least on

this one, you did, and you may do this to try to determine what's wrong with it. Maybe you've

already identified that, okay, this isn't actually starting, it's just cranking at a high speed,

and it gives up after about 15 seconds or so of doing that. Now I have to determine why. The thing

you want to be careful of here is that every time that you attempt to start this, and it spins the

engine for a period of time, you are draining the high voltage battery. And that's another piece

that you could look at to infer that it's just spinning the engine and not starting it, is your

high voltage battery voltage will drop every single attempt. And it is going to drop every

single attempt because the engine doesn't start. So it can actually charge the battery back up,

you are just draining that battery. And the problem with that is if you continue to do that,

you will eventually deplete the high voltage battery, which, yeah, it's not the end of the world,

there's ways you can either take this apart, put a new battery in there, you know,

charge it back up, if any of the cells are bad, all that stuff, but that's a lot of work, right?

You got to pull the battery pack out in order to do that. And if you're just trying to figure out

why this thing doesn't start, and the high voltage battery was not the problem in the first place,

but now it is, we've got to fix that before you go into the actual no start. And unfortunately,

that is something that happened on this one, because so many attempts had been made in order

to try and start this thing, that there wasn't much left to go. And then eventually got to the

point where clearing codes weren't even going to do. It would give like a small attempt to crank,

and then it would just say there was a different code that said the high voltage battery pack is

depleted. So then you had to either replace it or rebuild it or whatever you do to get that

high voltage battery pack back up, just so you can then attempt to figure out what's going on. So

another piece of advice on any hybrid no start. And I've talked a little bit about this.

Hey, have you ever been faced with the challenge of sourcing, installing and programming a used

control module in a vehicle? I know a lot of us have. It seems to be happening more and more often

today with the volume of control modules on vehicles, the cost of some new ones, or even the

availability of new control modules in some cases used may be the only option. So what do you do

here? I strongly recommend checking out SJ auto solutions and Tommy Oliva. Tommy offers a cloning

service for use control modules to make these things plug and play for the vehicle that you're

working on. In a lot of cases, he is also able to source the control modules if you're unable to

locate one for the vehicle that you're working on. But once you get connected with Tommy, he's

going to offer fantastic support from start to finish to make sure that that control module is

going to work in your application. He's also got tech support that he offers through his website,

along with some free resources there as well on information about used control module programming.

So make sure to check out SJ auto solutions. I can't recommend that enough.

Before two is you want to try and set up as many tests as you can and get them in one shot, right?

So if you've got a four channel scope, use all four of those channels for whatever pieces of

information that you feel you need to get, right? Are we getting injector pulse? Are we getting spark?

Looking at the maybe WPS in one of the cylinders, obviously looking at fuel pressure, all the stuff

that could prevent an engine from starting or at least give us info into why it's not starting.

And of course, there's a ton of different reasons why an engine might not start. It's just like any

other internal combustion engine. And if you're familiar with the Priests that are just like any

other engine, but again, you only have so many shots. And depending on the health of that battery

pack going into the diagnostic, you might be limited. And you can look at the voltage and kind

of decide where you're at there. But gathering as much data in one shot is important on these,

more so compared to just a 12 volt system where, hey, the battery dies, I'll throw a jump pack on

it and continue cranking. You can't exactly do that here. So something to consider. Now,

back to the car that I'm actually working on here, the no start on this thing. And we did have

problems with the high voltage battery. And they had to correct that for us before that we could

actually get to a solution. We had just about everything that we needed in order to start this,

as far as spark, good spark out of the coil, injector pulse, WPS looked really good, like

not a plug cat or anything like that and great compression, the waveform looked good there.

We had fuel pressure, had just about everything that we thought we would need in order for this

thing to start. And I should note, when this thing would, when you go to hit the key, and you

attempt to start this thing, you could hear some rattling at first. And I'm actually kind of wondering

if this is where the 3190 poor engine performance came from versus the 3191 engine failed to start.

Anyways, you could hear some rattling and then it would stop. And then it sounded like it was

just running. And I wasn't exactly sure what that meant. But I know on some of these Priuses,

because of the dampening device between the engine and the transmission, if you have a

misfire, these things will make a horrible noise that makes you think that the engine's going to

fall apart. But it's normal when there's a misfire on one of these. And I kind of heard that a little

bit. I'm like, well, maybe it's popping off a little bit. But it's very hard to tell compared

to a 12 volt battery cranking over an engine, compared to this high voltage Prius cranking

over an engine. It just, it doesn't sound the same as far as what I'm used to. So we went back

and forth on this one. And eventually what I ended up doing, because this is part of my process

for a no start, is I'll get a fuel sample. And I'll almost always do this when I hook up a gauge

in order to check the pressure is, hey, I'm right there, I've already got connected to the fuel

system, if I'm tying in a gauge. Now, of course, there are situations where you're looking at a

sensor on a scan tool, that's not going to apply, you're going to have to do an extra step to get

a fuel sample. But especially if I'm hooked up to the actual line, like I was in this one,

to check pressure, I want to check the actual sample of fuel to see what it looks like. And

many times contaminated fuel has been the cause. I'll also check another thing when it comes to

that is I will look at the gauge. Now, of course, look at the gauge, make sure it's not empty,

you probably want to feel pressure in that case, I did have pressure, but the tank is

completely full, like it's plumb full. And if you see a situation in a no start vehicle,

and it's just one of the things that I try to observe is, hey, okay, is the fuel

completely full, right? And this isn't a 100% thing. But let's say somebody put in fuel that

was a problem, they would, they're usually going to fill up the tank. And so a full tank might

indicate that, hey, there was a change as to what was in the tank just recently. Of course,

you can question the customer. It's a little bit more of a process for us to do that, because

we're going through our customer, which is the shop to then their customer, not to say that it

can't be done. But there's an extra step to it. Anyways, I take a look at that. I'm like, okay,

I definitely want to check the fuel sample on this one, because it is completely full.

And here's the other thing, it's a delivery vehicle. There was stickers on the side that

this Prius is actually, you know, being used as a delivery vehicle. And not that means anything

really, but what are the odds that somebody doesn't actually, you know, own this vehicle,

maybe they put in the wrong fuel. And maybe they didn't do anything wrong. It is possible

just to get bad fuel, depending on where you fill up. That's the other possibility. So anyways,

I want to fuel sample from this thing. And I pulled the fuel sample. And immediately,

I look at it, I'm like, Oh, this is not gasoline. And I can always say that from

many times doing a fuel sample, getting regular pump gasoline with about 10% ethanol here for the

87 octane here in Minnesota. And it has the regular gas has kind of a light yellowish tint.

And it's fairly clear, meaning you could see through it, I put it into a glass graduated

cylinder, so that I can do like an E 85 test. It's really easy to do there. But I'm looking at

I'm looking for sediment, something that doesn't look like gas. And this

does not look like gas. It's almost like a bright yellow, which is not the way that gasoline looks.

And if you're not following me on audio too much, you can Google this, and you'll see the difference.

But this to me looks like diesel fuel. Okay, now I'm not 100% sure. And the smell, it kind of

smells a little bit like gas. But my guess is that there probably is a little bit of gas in here.

It probably wasn't completely empty. But what is in there mixed with it is definitely not gasoline.

It's a it's a very different color. And it's almost a different consistency too. And again,

that's hard to transfer over audio on a podcast. But if you've seen enough gasoline,

you can pick out what's not gasoline. Now, if you're not sure, you could do the next thing I did,

which was kind of to prove it to the shop that this was not gasoline, is find a safe place,

pour a little bit of it out and try to actually light it on fire. Okay, so we went out back of

the shop, we just found a spot on the ground, poured a little bit of it out, took a lighter

up to it. And as I'm sure all of you know, if it's actual gasoline, it's going to go and it's

going to burn very quickly and very hot. If it is diesel fuel, it is not going to do that.

Yes, it will burn, but it's going to burn very slowly. It will be like the same amount of flames

as you lit like a piece of paper on fire. It's very slowly and it will just sit there with

little flames and burn. And that's what it did here. So it's a very different burn, because

diesel is meant to be ignited under super high compression, not in a gasoline engine with a

spark, very different things, right? Still trying to get energy out of the fuel through

combustion, but a different way of doing it. And diesel fuel is not going to burn gasoline engine.

And so we proved there that this is diesel fuel that's in this tank and it's, you know,

completely full. So you guys need to drain the tank and fill gasoline and clean everything

else out. And we recommended, you know, checking the spark plugs and the cylinders,

dry all that stuff out best you can. So they did that. And they said, yeah,

the tank was full. I don't know how they filled it with diesel, because obviously the diesel

nozzles are wider than the gasoline nozzles. But when there's a wheel, there's a way.

I don't know exactly how it happened, but I know that's what was in there. So anyways,

they cleared out, they get all back together and say, hey, this thing still is doing the

same thing. We're a little crank for a while, seem like it's running, and then I'll shut off.

And we tried a couple of times, but we don't want to drain the battery. We come back out

and check it out. So I come back out and I check it out. And I'm still pretty confident about what

I found. But I'm going back over to my steps to make sure I didn't miss anything. One thing I had

kind of skipped over was like an EGR being unplugged, or I'm sorry, an EGR being plugged open

could cause something like this. Look at my sensor values and everything looks like it's there. And

now I actually have, you know, quality gas running up to this thing with good fuel pressure.

But the one thing that they didn't do is actually change the spark plugs.

They took them out and they dried them off. But what ends up happening there when those

things get soaked with diesel fuel is they're not going to work there. If they're fouled out, and

is it impossible to get them working again? Probably not. But just put a new set of spark

plugs in there. So they did that. And then it fired right up immediately after that. And again,

I took the spark plug and I held it up and I put the lighter across it. And you can see it's wet.

And it's not burning like it's like you dipped it in water. And I was like, get some new spark

plugs for it. So I know those are maybe low tech tests to run. I think you can do a specific

gravity test if you really want to figure out if it's diesel or gas or whatever mixture. But

I mean, those those tests work and they prove it and they can prove it to the person standing

there of like, Oh, yeah, this is not gasoline. So diesel changed out with gasoline and a new

set of spark plugs got this one to start. But I thought what was more important on this

to get out on the podcast was the couple notes about the no starts in hybrid vehicles like this

where you may think it's running, but it's not. Pay attention to the codes, pay attention to the

data pins, look at the exhaust temperature. And also with that, be aware of how you're draining

down the high voltage battery as you're attempting to start it, get as much info as you can from

each attempt. That's what's really important on this one. So that's where I'm going to wrap this

one up. And thank you, everybody for listening. I really appreciate it. But that all out of the way.

Let's get out there start fixing the world one car at a time.