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3 Trouble Codes To Not Worry About On Your Toyota Prius

We all get them from time to time. Trouble codes can be Prius owner's worst nightmare. Here are 3 codes you should be aware of but not overly worried about.

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I love trouble codes, said no one ever. I have not yet met one Prius owner that wants to have issues with their car. Well, maybe, I do. I am crazy like that, though, because I learn from what these codes mean.

After driving many of these aging Prius' now, I have found there are just some engine codes you do not need to stress over. Now I am not saying to leave them, for sure, get the problem fixed, but if you cannot do it right away, try not to worry.

Trouble Code 1: P1116 3 Way-Coolant Flow Valve
Second-generation Prius, model years 2004-2009, has a 3-way valve to control coolant flow between the engine, the hot coolant storage tank, and the heater core. It is involved with heating the passenger cabin, as well as reducing cold-start emissions.

Toyota Prius P1116 Trouble Code 3 Way Coolant Valve

If anything on Prius has to do with emissions the “check engine” light will illuminate; if something goes wrong with this valve, the light comes on. The control valve is prone to seizing, and Toyota has issued a technical service bulletin (TSB) on this problem: EG001-08 M.I.L. “ON” DTC P1121.

The fix is replacing the valve. The reason you do not need to worry too much about this trouble code is that it will not keep your Prius from running. It will not cause it to stall out. It is emissions-related, and hence it sets the trouble code to help you know that your Prius is not running at peak operation. Do not sweat it, but do get it fixed, especially if you are in an area where emissions testing is required.

Trouble Code 2: P0138 Oxygen Sensor Circuit High Voltage Bank 1
When you have a sensor fault, you need to be aware your car is trying to tell you something. Again, get your Prius in and have it seen, but do not fret if you cannot get it in as quickly as you would like.

Toyota Prius Oxygen Sensor P0138 Trouble Code

This particular code, while not as nearly popular or common on Prius, can happen. Take a look at this article here, where I strangely solved this code. This code can happen for many reasons, but again, it will not cause you to stall out or leave you stranded. Best not to worry, but do get it fixed.

Trouble Code 3: P0420 Catalyst System Efficiency Below Threshold
Yikes, I hate this code the most, and with all the crazy stories about catalytic converter theft these days, no Prius owner needs this. A P0420 means that your cat converter is not able to work effectively anymore.

Toyota Prius P0420 Catalyst Efficiency Below Threshold

When this happens, you will more than likely need to replace the converter and get back on the road again. The P0420 is another code that you will need to get taken care of but still will no cause your car to stall out or cause you to be stranded.

You will need to have it fixed for emissions testing purposes, and having a cat that works does keep our air cleaner. If you have to drive your car and cannot afford the fix right away, get it done when you can.

Trouble codes do mean trouble, but not all codes are reasons to panic. Make sure you get your Prius checked out as soon as possible. Your Prius will give you many trouble-free miles of driving if you take care of it, which you should be doing. If you cannot afford the fix at the moment, save the money get it done as soon as possible.

Thank you for reading. See you in the next story. Which Toyota wears the fuel economy badge better?

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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.

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Gloria Lynn (not verified)    November 16, 2020 - 9:44PM

Ok. So I have an 05 Prius. I have already reached the coolant flow control valve position sensor, and I just recently replaced the engine coolant temperature sensor for coolant heat storage system because that's what I read to fix for the P1116 code. It's only 2 days later and my engine light is back on again with the same code. What is this valve you are talking about replacing? I'm so tired of my engine light being on! I also get the P0420 code now and then, not every time though. I used a fuel cleaner. I haven't seen that one again yet, but waiting to see. Please help!