What You Should Be Concerned About The Most If You Buy a Used Toyota Prius

I do not know one person on this earth that would ever say, "I am sure glad I got ripped off buying a used car." In fact, I think that it would be quite the opposite. When I bought my Prius I knew what I was getting into. I knew that it had a faulty traction battery, a bad catalytic converter and a few other issues.

I would say many people do not have the skills that I have or know what I know. This can make getting into the Prius of your dreams quickly become a nightmare. I will to put down all the data that I am aware of about the top three generations of Prius (1st, 2nd and 3rd) to help those who are looking (or already own but may not be aware) of things to watch out for as far as common issues when looking to buy one of these little gems.

Toyota Prius Generation 1

AKA First Gen, this Prius was the pioneer that started it all. It came with a 300v nickel metal hydride battery and a sweet 70 horsepower gasoline engine. Overall, combined with the 44 horsepower electric motors we had a whopping 108 hp that was a little less than enthusiastic.

With all this new technology came a new world of issues, though many problems did not rear their heads till well after the second generation was out. Still, if you are considering a First Gen, here are some common things to look out for.

The traction battery.

As you will see, I will talk about the battery in each iteration of Prius. They all have issues but they did get better in each segment. First gen modules were not made with extra cooling on them and after awhile they were subject to too much heat and would inevitably fail. As these modules were also a new style of battery they had another issue. These batteries also were prone to leaking and causing high voltage isolation faults, and battery trouble codes. Even though Toyota made a valiant effort to take care of the owners some of these cars slipped away untouched by technicians. Be aware that the First gen batteries can still be out there and can cause issues.

The transaxle.
The hybrid transaxle is a power split system. This basically means that the gas engine and electric motors can run independent of each other. When Gen 1 Prius came out, the transmission fluid that was available for the time period was Toyota Type T-IV (Type 4). The issue with this is that this fluid was not an isolation fluid. This meant that as the fluid began to break down, it would allow electricity to flow through it. This ended up causing stator burn out on one of the motor generators (MG) and the vehicle would drive very rough. The fix for this problem was an updated transaxle and a better fluid we now know as Toyota WS or World Standard. It has better isolation properties and now other generations of Prius have better reliability.

The electric power steering.
If I have said it once, I have said it a hundred times. New tech brings new problems. Electric power steering was a relatively new thing back in the early 200's. Gen 1 took the brunt of the fall for the issues surrounding this new technology. Toyota went as far as even recalling over 52,000 1st Gen Prius because the the motor units were suddenly not working, most of them when turning left. Sadly, only some of these cars actually made it in to have the repair done. Beware that the little old lady next door who has a pristine First Gen Prius may not have had any of the common issues taken care of.

Toyota Prius Generation 2

Often hailed at the "gold standard" for the Prius, 2nd Gen had major improvements. We dumped the 300v battery in favor of a 201.6v battery with a boost converter. We also now had a 76 hp motor and 67 in the electric motor. Now at 143 combined horsepower, we had a little more to play with. Improvements in the battery were also made. The modules were ever so slightly larger and now had a silver coating on the side that allowed for better heat dissipation. Even though 2nd Gen had improved, it still had issues.

Traction battery 2, return of the battery
The battery improvements as stated above were helpful. The boost converter really was an awesome feature that helped Prius zip along at a steady cruising speed even when battery SOC was low. So why do we see so many 2nd Gens have battery issues today? While the improvements were good, Toyota did not account for the actual life cycle of these things. They did warranty them for 10 years or 150,000 miles in some states, but often consumers fell prey to the dreaded battery degradation. Extreme climates are a big factor. The master warning light, or as many know it, the triangle of death, has meant to many Prius owner, (this is not exclusive to the battery) that the HV system was in trouble. Note: The master warning light can set for a plethora of reasons not just for the hybrid system, please drive responsibly.

The reason I believe we still see so many battery issues on Gen 2 is just due to the sheer number of them on the road still. 2004-2009 was an era for Prius that has been legendary. Just be aware that if you are in the market for one of these, make sure you have someone who can check the health status of the battery first before purchase.

Inverter/Converter Coolant Pump Failure
This recall put out by Toyota was to solve issues regarding internal inverter pump shorting/failure. This could cause the pump to completely stop working and blow the AM2 fuse which would cause the vehicle to not start again. It was protecting itself from overheating and inverter failure. Some of the Gen 2 Prius made it into the dealer and some did not. A quick VIN upload to Toyota's recall website can tell you if you have any open recalls on your Prius. It may be wise to check before purchase, though I have not seen a Gen 2 in the past 6 years have an issue. Still something to look out for. Should you experience it today, try bleeding the cooling system and using the proper coolant to see if that fixes the issue. Sometimes air can become trapped in that part of the cooling system and also cause the P0A93 code to appear as well.

Oil Consumption and rough start/stop
The 1NZ-FXE 1.5 liter engine is a trooper. The little engine that could is a true story when it comes to Prius. 1st and 2nd Gen both share the exact same engine, and also a similar problem as well. During the massive amount of starting and stopping that happens, the oil takes a fair beating. Most consumers, while I am sure are well intentioned, fail to sometimes get that oil changed on time. This is a huge problem. When engine oil breaks down, the remnants of it, hard carbon deposits, build up inside the engine. This means that in the VVT-I solenoid which is utilized for late intake valve closing can become plugged up and cause a hard start. Furthermore, the carbon builds up in the piston ringlands as well. This causes lack of proper sealing in the combustion chamber and leads to high amounts of oil consumption over the period of the oil change.

Make sure when you are on a test drive for your potential 2nd Gen, pay close attention to how it starts and stops, it if is really rough, it. I would steer clear of something like that because it could cause you more trouble than it is worth later on.

Toyota Prius Generation 3

The thirst for continuous improvement never ceases at Toyota Motor Corp. Gen 3 as it is commonly known, was the implementation of new and proven technologies. We now know that not all new things are good and this was certainly true of Gen 3.

Traction battery 3, a respectable new hope
The battery remained the same in this model year despite some new computers that were governing it. the same 201.6v Ni-MH battery was the exact same proven tech that was found on Gen 2. We still see battery replacements happening on this generation of Prius as well. It is not uncommon to have the same battery failures as we saw in the previous gen, but that was to be expected since it is basically the exact same battery tech. Again, have the battery tested. You can also do this by driving the vehicle hard and seeing how fast the battery monitor drops on the screen. If the battery falls quickly (10 to 15 seconds heavy acceleration) the battery is pretty weak and will need to be replaced soon even if it has not tripped a trouble code just yet.

Inverter/Converter Failure
Due to a manufacturing error in the plant, the converter/inverter has been known to fail on some early Gen 3 models. Typically 2010-2012. The inverter when assembled used a thin film of heat paste that allowed it to be cooled evenly across the electronics inside the unit. The paste on some of the units was not spread on correctly. This would result in a shut down or permanent set trouble codes which would not allow the car to drive normally. Maybe just a short distance to the dealer.

Toyota has been under fire for this for quite a while now and has even had a few recalls on them too. If the car you are driving has any codes related to the inverter assembly, do not buy it (unless it is a killer deal) because the cost of repair is going to be between 2 and 3 thousand. That is if Toyota will not cover it.

Oil consumption/misfire
Gen 3, even though it had a new 1.8 liter engine which was more powerful and efficient, it now is plagued with issues. If you look at the oil consumption issues 3rd gens are facing, it is very similar to what we are seeing in gen 2. One of the major contributing factors here is the fact that is causing this (besides starting and stopping all the time) has been the addition of the EGR (exhaust gas recirculation). EGR helps lower combustion temps for less harmful NOX outputs from the tailpipe. It is a way to clean up the exhaust without adding in larger more expensive catalytic converters.

The issue here again is carbon. Carbon is plugging up in the ports due to oil breaking down and not being able to suspend the deposits then filter them out. Once oil breaks down like this, deposits form very easy, once this happens we no longer can seal the combustion chamber. This leads to consumption and early cat converter failure as well. Also the replacement of the PCV (positive crankcase ventilation valve) is a huge help.

The PCV which circulates blowby gasses back into the intake manifold for reburning, carries a certain amount of deposits with it. As the oil breaks down, those deposits can cause the valve to get stuck open allowing oil to puddle into the intake manifold. This also can cause engine misfires and poor drivability.

Conclusion

Despite all these issues, Prius is a very reliable vehicle. All of these issues are fixable and more than likely will not happen again if the vehicle is maintained properly. I love my Prius and hope to get another one here soon. I am building a fleet of them for my upcoming classes that I will be holding. Before you buy, please get an expert's opinion on the car, and no, Scotty Kilmer is not a reliable source. Feel free to reach out to me on social media through the Toyota Prius Owners Club and ask for help.

I hope that you have enjoyed reading about What Should You Concerned About The Most If You Buy a Used Toyota Prius. 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 the Toyota Prius AWD-e is the best one yet and why car enthusiasts and average car guys loathe the Toyota Prius. Also, read my latest story where I am discussing why Toyota Prius hybrids are so durable.

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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 can be reached on Linkedin and you can tweet him at The_hybrid_guy on Twitter.