Toyota Prius 12V Charging System Functional Test

John Educator Ogden, Utah Posted   Latest  
Demonstration
Electrification
Electrical
2017 Toyota Prius Two Eco 1.8L (2ZR-FXE) (P610)
12V Battery (Auxillary Battery) Low Voltage
No Ready Lamp
Car Shuts Down While Driving

In preparation for a Hybrid and Electric vehicle class I was teaching in July, I decided to try and find the procedure for testing the output of the DC-DC converter (The equivalent of an alternator) on Toyota Hybrids. I discovered that it has been the same procedure across all four Prius generations here in the U.S.A.. Depending upon the model year, the procedure is found under Power Source / Network - Charging System section of the Toyota service information. It can also be found as the last step in some DC-DC converter DTCs. The procedure was somewhat confusing for me comprehend, but after trying it a few times it made sense. I decided I had better document the procedure before I forgot how the test is supposed to be performed. 

I believe this test procedure will work on just about any hybrid or electric vehicle if you can access the correct cables. It is my understanding that the DC-DC converter should always be able to supply enough current for the total vehicle electrical load (an unmodified vehicle) as well as charge the 12V battery at the same time. 

I will be researching other hybrid and electric vehicle auxiliary battery charging system tests during the coming semester. I will let you know if I find anything significantly different.

Is your Prius 12V battery going dead? Learn how to check the on-car 12V charging system (DC-DC Converter) with this video. youtu​.​be/_V9PiOpaxyE&nb…;

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Michael Owner/Technician
Rochester, New York
Michael
 

Great job John. I like seeing this content. I feel like my knowledge of Hybrid vehicles is not where I want it to be. I like to absorb whatever I can and appreciate you sharing your knowledge. In your video you said that the older gen Prius‘ seem to draw a lot more amperage with the headlights on. Do you think that the newer ones draw less due to them using a LED bulb system vs the high

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John Educator
Ogden, Utah
John
 

Thank you! The second generation Prius uses HID headlights, and the third and 4th have optional LED headlights. The LED lamps draw much less current.

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Dr. Engineer
Port Angeles, Washington
Dr.
 

Hi John: Very informative video and thanks for all of the time & effort to go through Toyota's process. However, I think an alternative (and overall more technically sound test) that may provide some additional findings would be to use a load tester and an oscilloscope. Although Toyota prescribes a different process, when testing power electronics (whether automotive or otherwise) loading

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John Educator
Ogden, Utah
John
 

Hello Mark, Thank you for your remarks, great suggestions, and additional information. I was not aware of dual channel DC-DC converters, but it makes sense. The Toyota method in the video has the technician turn on all of the electrical circuits possible in the vehicle to load the circuit. This method of testing could be run for hours if needed while watching scan tool PIDs of temperature…

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Dr. Engineer
Port Angeles, Washington
Dr.
 

Hi John: Please see my responses to your questions: 1. What do you suggest for a external variable load tester that would not overheat over a long period of time? Purchase a blower to increase airflow through the unit. If the correct minimum amount of airflow is utilized then, the unit will not overheat. I haven't calculated what you would need but, it can be calculated and an auxiliary

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John Educator
Ogden, Utah
John
 

Hi Mark, Thanks for the additional information. I will try the additional cooling fans for now. I am interested in a programmable load tester for DC-DC converters. It cannot be a magic box with a pass or fail (Kent-Moore Tool Style), it would have to produce useful data and be user adjustable with different settings. The cost would need to be lower than $1500 or the school cannot purchase it

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Dr. Engineer
Port Angeles, Washington
Dr.
 

John: You may want to think about using something like a flexible plastic (corrugated) hose to go between the blower and load tester. The hose will need some type of adaptor to the blower so the can be pressurized hose can be pressurized (ditto for the load tester side of the hose). Or, just make an adaptor with no hose?? I did some "back of the envelope" (nothing super scientific) CFM

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Jim Manager
Portland, Oregon
Jim
 

Hi John, Thank you for the excellent study. I have a challenge for you regarding DC-DC activation strategy on the Honda IMA platform. Here is our story. Well over 10 years ago we were presented with a (not running) Gen 1 Honda Civic Hybrid with a depleted IMA battery (that had been condemned elsewhere), a depleted 12V battery, and a used IMA battery protruding from the trunk. We charged and

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John Educator
Ogden, Utah
John
 

Hi Jim, I know exactly what you are talking about. I probably receive two email or YouTube comments a week from someone with the Honda IMA system, a bad IMA battery, the 12V battery not charging, and the engine stalling while driving. Of course they have already changed the 12V battery and it did not fix it ;). This is a huge problem on pre-2014 Honda IMA hybrid systems. I do not know the exact

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