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5 Top Trouble Codes In Toyota Prius And A Sure Fire Way To Fix Each One

When working with a highly complicated car like the Toyota Prius, trouble codes can be a scary thing. Or are they? Here is how you can deal with trouble codes on your Prius, like a boss.


If I were to take a poll with Prius owners, I would bet that most of them have encountered at least one trouble code in their car. There are millions of Gen 1, 2, and 3 on the road without warranty, and the cars are aging. The more Prius gets used, the higher the risk of getting a trouble code for a failed part.

When we get the master warning light that comes on in Prius, it can send a shockwave of terror through us, not knowing what has happened to our car. I want to cover 5 top "check engine light" problems that can occur, and fixes that are not guesses, but proven repairs for your Prius.

Top Repair One: P0A93 Inverter Cooling System Performance Code
I have seen many people who get this code and initially almost have a come-a-part. While no one likes their car breaking down, with this code, there is not a reason to panic. The code is quite common, and the repair is easy.

This code is widespread in Gen 2 Prius. While the service manual states there are several causes for this code appearing, it has been proven over time that the right repair for this is merely replacing your electric inverter water pump.

Toyota Prius inverter water pump

The reason that trouble code sets is due to an internal pump failure typically found on the motor windings. This "short" causes momentary pauses in the impeller flowing and then sends a code to the computer with the corresponding trouble code.

If you get the P0A93 code, you only need to replace that pump and move on. It is a fast and straightforward repair that can be done in less than an hour. I have a full write up of this specific code found here if you would like to know more.

Top Repair Two: P0420 Catalyst System Efficiency Below Threshold
A P0420 trouble code is our next one here. If you have had your cat converter stolen, this code and others would appear along with a droning noise, letting you know that part of your exhaust is missing.

A P0420 trouble code means that your catalytic converter is not "firing" and converting those harmful exhaust gasses into lesser harmful gasses. The catalytic converter is a vital part of the low emissions system that Prius has.

Toyota Prius Catalytic Converter

The trouble code sets because the oxygen sensors are not seeing enough oxygen storage inside the converters. The sensors are doing their job if they detect low oxygen. The corresponding code is then sent to the computer, and you get a check engine light.

Cat converters can fail in many ways. A lot of short trips or oil consumption in our Prius can cause build up on the precious metals inside the converter over time. This buildup reduces the overall efficiency of the converter.

Unless your cat converter is missing, there is not a huge reason to freak out over this code. Your Prius will still run okay; it will not pass emissions testing, though. The fix for the P0420 code is replacing the converter, that is it. Do not bother getting it diagnosed; just replace it.

Sometimes, there are other causes for the code, but they are infrequent and not likely going to happen on Prius. For more information on catalytic converter theft, check out this article here.

Top Repair Three: P1121 Coolant Flow Control Valve Position Sensor Stuck
Another contributor to our check engine light list of failures and a common one is the P1121 code. This code means one thing, replace the three-way coolant valve.

P1121 is another code that appears on Prius regularly. The coolant valve gets stuck, and it only needs replacement along with some coolant. This code will set from a valve that has seen some use in its day. It will not harm your car, but it will tell you that it has failed.

Toyota Prius 3 Way Coolant Valve

The repair can be done in less than 2 hours and for not much money. If you get this code, replace the valve and continue driving.

Top Repair Four: P0A80/P3000 Replace Hybrid Battery Code
A P0A80 can occur for many reasons, but what the Prius is telling you is that your hybrid battery is not working as it should. A P0A80 is a signal that you need to replace or repair your hybrid battery.

People often get confused about what to do with a P0A80 when all you need to do is get a new battery. There are people from the DIY crowd that will want to repair the battery, which is okay, but that does not mean that it changes why the code appeared.

Toyota Prius replace battery code, means replace battery

A P0A80 sets because of hybrid battery failure, period. The reasoning behind the fault can be for several reasons. If you are someone who is not mechanically inclined, replace the battery and move on.

If you are a tinkerer like myself, then use the Dr. Prius app and find out what has happened to your battery. Repair it and move on.

Top Repair Five: C1256 Failed Brake Actuator Code
If you get a long buzzer and a master warning light, chances are you have a C1256. This means you need to replace the brake actuator on your Prius.

The reason this occurs is that the brake system can no longer maintain pressure internally. Could you have another issue with your Prius? Of course, but when this code sets, just plan on getting a new part.

This repair is the most complicated out of all the others, and I would recommend taking this one to a shop that has the proper equipment to repair your Prius.

Could I be wrong about these codes? Sure, I could, but the thing is this, Prius is very well built. If you get this problem, someone else has it too.

I can say with confidence that If you get these trouble codes, your repairs may not be cheap, but there is almost ZERO guesswork on what is wrong. Take it from an expert who has to spend a lot of time repairing these cars; they are not that complicated to figure out.

Happy driving and I will look forward to seeing you in the next story. Save Thousands On A New Toyota Prius By Doing This Search

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Peter Neilson is an automotive consultant specializing in electric cars and hybrid battery technologies. He holds a Bachelor of Science in Automotive Service Technology from Weber State University. Peter is also an 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. Find his page on Facebook at Certified Auto Consulting. Read more of Peter's stories at Toyota news coverage on Torque News. Search Toyota Prius Torque News for more in depth Prius coverage from our reporters.


Joan Myers (not verified)    June 28, 2020 - 2:00PM

My warning lights are all lit on my 2005 Prius and the garages computer does not show a code. I am thinking it is the 12 volt battery!

Shonna Jolicoeur (not verified)    July 17, 2020 - 2:47PM

Someone stole catalytic converter out of my 05 prius. Had that replaced along with 02 sensor. When i went to pick it up everything was fine until i got ip on the freeway. All of a sudden i had the car start to slow down and the red tryangle, brake system warning light, check engine (malfunction indicator) light, and the VSC light came on. I have hooked up obd2 to car but no codes come up. I am disabled and cannot afford to take it to Toyota dealer. Any ideas. Thanks for help.

Kaitlin Haskins (not verified)    April 3, 2022 - 1:09AM

In reply to by Shonna Jolicoeur (not verified)

Shonna: What was the outcome with your Prius after this point in 2020? The same thing happened to me after the catalytic converter was stolen from my 2009 Prius. Ugh. I’m currently trying to figure out what to do.

Zahir shah (not verified)    February 12, 2021 - 5:29AM

In my prious car 2008 model some time all codes coming and some days not coming all codes what's the fault

Richard Cook (not verified)    April 6, 2021 - 11:00PM

I have an 02 Prius, when I start the engine it runs fine for about 10 seconds, then the drive wheels oscillate forward and backwards for 1 second intervals and does not quit. I'm having trouble finding anyone that has heard of this. Any thoughts?

KAREN COBB (not verified)    June 30, 2021 - 5:17PM

I have a 2005 prius and that little computer light that show the heater radio well it dont come on I took it to shop an 801 show up he told me to take it to a dealer I have look everywhere to find that code cant do u think it a bad or can u direct me where i could find that code thank you

KAREN COBB (not verified)    June 30, 2021 - 5:25PM

I have a 2005 prius and that little computer light that show the heater radio well it dont come on I took it to shop an 801 show up he told me to take it to a dealer I have look everywhere to find that code cant do u think it a bad or can u direct me where i could find that code thank you

Barry (not verified)    July 28, 2021 - 7:41PM

Saying that the only cause for P0A80 is traction battery failure and you should simply replace or repair the battery is silly. P0A80 can be secondary to other codes and failing to say so is misleading. Some owners may hear an "expert" make this statement and park their car because they can't afford to buy a new battery. Others may simply order the new battery when it may be unnecessary.

alalin (not verified)    October 10, 2021 - 12:51PM

Bonjour j'ai les codes suivant
$07E8 moteur
Quelq'un a déjà se problème et ou pourriez vous m'expliquer merci

Leonevalc (not verified)    March 23, 2022 - 1:59PM

I have 09 Prius and it got 105k miles already. The problem is the chk engine P1116. I have obd II just to erase temporarily. My mechanic has tried and tired of replacing parts/ sensors to no avail. Help !!!

Leonevalc (not verified)    March 23, 2022 - 2:03PM

I have 09 Prius and it got 105k miles already. The problem is the chk engine P1116. I have obd II just to erase temporarily. My mechanic has tried and tired of replacing parts/ sensors to no avail. Help !!!

Chandra Pounds (not verified)    June 6, 2022 - 2:39PM

I bought a 2006 prius & I wish I didn't now the check engine light the triangle came on & the red car on screen came on with a line threw it & it died what can I do to fix it I wish I could take it in & trade it

Pamla Crouch (not verified)    September 12, 2022 - 11:50AM

I have a 2005 Toyota Orius that shows codes p1121 and p1116. The check engine light goes on but it also still heats up the cabin and it also goes off by itself. Its due for inspection what can i do about this. Also the tear driver brake light is dim but still works is there a quick fix for this or do i need a whole new light.