Modifying Toyota Prius HV ECU

May 7, 2024
Some 2016-2019 Toyota Prius vehicles equipped with a NiMH HV battery may exhibit one or both of the following conditions after repeated driving on long downhill slopes.

Some 2016-2019 Toyota Prius vehicles equipped with a NiMH HV battery may exhibit one or both of the following conditions after repeated driving on long downhill slopes or while driving in high ambient temperatures, then turned off for about one or two hours and restarted:

- When accelerating from a stop or from extremely low speeds, the vehicle may have a reduction in power.

- The HV battery monitor on the multi-information display continually shows one bar, indicating that the battery state of charge (SOC) is at it’s lowest level.

The Hybrid Control Computer (HV ECU) logic has been modified to reduce the possibility of these concerns. If the fifth character of the VIN is a “B” or a “9”, reprogram using software version 14.20.019 or later. During reprogramming check for the new calibration number based on the vehicle’s current calibration.

About the Author

Motor Age Staff

Motor Age has been publishing technical content for professional automotive technicians since 1899. Our writers have decades of experience and scores of ASE certifications, and they continue to teach new generations of technicians via classrooms all around the globe, as well as through the books and training manuals they've authored. 

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