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Pro Tip: Do This Before Buying A Used Toyota Prius

If you are leery of buying a used Toyota Prius, here is a tip that can help you know if the car is OK.


Buying a used Toyota Prius can be a nightmare. I literally had a short conversation with someone who bought one, and the battery went bad 30 minutes later.

It got me thinking, what could I help people look for to know if the car is at least ok to take for a test drive. I came up with an excellent "pro tip" to help you all out.

Toyota Prius Readiness Monitors
If you are not sure what a readiness monitor is on a Prius, it is not complicated. It is not the "ready" light; it is something different.

Readiness monitors are basically a series of systems that monitor what the car is doing. If something goes wrong, the check engine light or check hybrid system pop up and tells you, "Hey, something is not right here."

OBD2 Code Check Device

The codes generated in the system are not the answer to your prayers but rather a guide to what system is having issues.

Ok, so how does this help? Glad you asked. When a trouble code is present, you have to clear the code so the system can "check" itself again. When you do that, the monitors have to relearn what they once knew.

This memory wipe would show up in the scan tool as a "Not Ready" situation, saying that the systems have not been through their testing to know if they are or are not ok.

Knowing this information can save you a trip down money pit lane, and here is why. If you ask to see the vehicle's readiness monitors, you will know if the car has been driven long enough for it to "self-check" all the onboard systems.

If the system is not ready, find another vehicle. This could indicate that the person or dealer who is trying to sell the car to you has cleared the codes. No one wants to see a check hybrid or check engine light on, so removing it can give them just long enough to take you on a trouble-free test drive.

There is a caveat to all this. What if the battery was recently replaced? That will wipe the memory as well. Ask questions and try to understand as best you can why the monitors are not set.

If the seller or dealer gets uptight about it, walk away. Chances are if they are getting bent out shape over something like that, they are probably hiding something.

The last thing I would ever want is for someone to be taken for a ride in a car that will destroy them financially. Have questions? Follow me on Twitter @the_hybrid_guy. I am happy to help you wade through the confusing details of buying a used Prius.

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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 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.


Gedster314 (not verified)    April 3, 2021 - 11:05AM

Pretty generic suggestion, that applies to all cars and is not Prius specific. Also, many cars have data pid that will tell you how many miles and hours since the last code reset.

People if you drive a car, buy a bluetooth obd dongle. At the very least pull the codes, google them and even if you are still taking it to a shop, you will at least be able to tell if the shop is blowing smoke up your butt. The dongle can be had for under $20 on Amazon and Android OBD reading software can be cheap. For car shopping I use ToyoSys for Toyotas, it's $2.99 for the pro version. Ain't fancy but it is reasonably quick. It clears codes, shows readdiness monitors and gives many live data pids. I like looking at fuel trims, O2 sensors, cam timing at idle to get a feel of the condition of the motor. There are better obd apps but I like that one cause it is faster. For car diagnosis, I have better apps and devices.

If you are in the market for a Prius or other Toyota hybrid get the DR Prius app, it has a test process that can give you an idea of the condition of the battery. Probably want to do an extended test drive, pull over and do the test away from the owner. The test requires full throttle for a few minutes, I can't imagine an owner would like seeing that.

Above all, once you find a car you really like and want, get a pre purchase inspection from a mechanic that knows those cars. Yeah, $100-200 for an inspection is a bitter pill but it may give you more ammunition to beat the price down some more and you will know what maintenance to do once you get the car home.

Dave Rittner (not verified)    April 3, 2021 - 6:03PM

This is no different than any other car equipped with OBDII, hybrid or not! The potential buyer must also have a scan tool that's capable of actually checking monitor status. Why pick on the Prius?

Matt (not verified)    April 6, 2021 - 6:51PM

In reply to by Dave Rittner (not verified)

This comment is sort of like reading an article about issues with Fords and then asking why Fords are being picked on when Chevys have the same issues. He's talking about the Prius, so naturally that's what he's going to focus on.