Skip to main content

If Your Toyota Prius Is Not Starting, This May Be The Cause

There are many reasons that a vehicle will not start, but when it comes to a hybrid like the Toyota Prius, it can easily get more complicated. Here is one common issue that happens more often than it should and can easily cause a no start condition on your Prius.


As a professional and an instructor it is crucial that I stay as up to date as possible. I attend trainings all the time from other industry professionals that teach on specific topics. This helps me to better understand my role as learn so that I can help the community of people around me.

The most recent training that I did was from a group called ATG (automotive training group) and it was on hybrid systems and operation. The manual they gave us was over 400 pages of in depth content that really helped me gain more into the Prius world I live in.

What Jeff, the instructor shared with us was priceless. We confirmed that Prius cars are so darn dependable that it is easy to figure out what the common issues are.However, there are times when un-experienced technicians work on these cars and get caught up in a very simple oversight. He gave us one killer thing that we all need to be aware of when doing maintenance on our Prius vehicles.

Do Not Overfill The Engine Oil On Your Toyota Prius

Yes, in the owner's manual for Prius it will tell you what viscosity of oil to use, and also the capacity. It also tells you to use the exact amount, but it never says why. Many Prius vehicles use less than 4 quarts (capacity varies between generations and engine types) and because of this, when refilling it is easy to add more than is required.

What happens when you overfill a Prius on engine oil is it can cause a no start condition. This seems silly but it is very true. The question is now, why this happens and what you can do to avoid it.

Overfilling Engine Oil Results In A No Start

Prius us ultra sensitive to how much engine oil is in it. The reason being is that it wants to have as little internal resistance as possible. This allows it to have the best possible fuel economy. When you overfill it, additional oil can get caught up on the crank (which is already pressurized) and flung up into the combustion chamber. This will result in consumption of engine oil as well as reduced economy.

adding engine oil to car drawing

Toyota has built in sensors, such as a resolver to help determine absolute position of the motor generators. If the resistance values change even a slight amount as the car gets ready to start, it will not, if it senses too much resistance from the additional oil. Note: this is Jeff's theory on how Prius senses the additional oil. It makes sense though.

What You Can Do To Avoid Overfilling

If you are a DIY person and want to change the oil yourself, awesome. I like to use quality products like Amazon Basics engine oil, and a Wix XP synthetic filter on my Prius(2007 Touring). I can do a better synthetic oil change than most quick lube places. My caution to you is this. Ensure you are putting the exact amount in that the system calls for. Measure out the 3.75 qts or whatever your spec is (that spec is 2nd gen Prius and I believe 1st also) and put that in. Start the car, let the ice run and check for leaks.

topping off fluid in car

If it shows below the top dot on the stick, do not and I repeat do not add more oil. Once the ICE runs, it allows oil to be put into suspension and dispersed through the engine. So, right when you shut off the car, the oil still has to flow back into the pan to get and accurate reading. The best solution is to let it sit for as long as you can (overnight is the best but not always realistic) but a few solid minutes will give you a much better reading.


Just be careful when taking your Prius in somewhere. I personally change my own engine oil and am very specific about my quantities. Please, if you do not know what you are doing, save yourself the headache and go see your dealer or your nearest (trusted) quick lube place for help. If they do not know the exact quantity of oil that should go in your Prius, do not have them change your oil.

As always, feel free to reach out to me on social media if you need help. Have a great start to your weekend and I will see you in the next story. I wanted to tell you all be sure to check out my favorite 3rd gen accessory right now which is the Nimbus Phone Mount, found on Amazon.

Check out my other story Why the first generation Prius is better than either generation Nissan Leaf.

See you in the next story where I am discussing why Carista is the best $20 tool for your Toyota Prius.

Also Watch New tech means more MPG from your Toyota Prius and Click to Subscribe to Torque News Youtube Channel for Daily Toyota Prius and Automotive News.

Peter Neilson is an automotive consultant specializing in electric cars and hybrid battery technologies. He is an automotive technology instructor at Columbia Basin College. He holds a Bachelor of Science in Automotive Service Technology from Weber State University. Peter is also an Adjunct Instructor of automotive technology at Columbia Basin College. Peter can be reached on Linkedin and you can tweet him at The_hybrid_guy on Twitter.


Fadel (not verified)    June 7, 2020 - 12:59AM

Hi 2910 Toyota Prius first was crankshaft sensor code and others code with message check hybrid system the OBD GAVE US P2135
We change the crankshaft sensor now the warning sign is gone and the car still not able to start the engine the 12 volt battery reading is good I don’t know what to do next.

Sharlie Busboom (not verified)    February 14, 2021 - 3:50PM

I have a 03 Prius and when I turn it over I get dash lights but no cranking, I replaced the 12 volt battery still no cranking!

James Saxon (not verified)    October 9, 2021 - 3:44PM

My ready light on my 2003 prius will come on and crank engine, but when turned off and try to crank it again, the ready light will not come on. I can remove the neg. battery cable and wait a few seconds and reconnect it and then get the ready light again. This happens almost every time I go to crank it up. 12v battery is fine, don't know what else to check.