Toyota Hybrid Synergy Drive Problems


When you own a Toyota car with Hybrid Synergy Drive, you might want to know how it works, what exactly goes under the hood and how this car balances both gas and battery energy. Here are the answers to everything you need to know about HSD and the solutions to the problems you may come across, with some useful tips on how to handle them.

Toyota Hybrid Synergy Drive Explained

For those of you who purchased the vehicle and don’t know what it means – the term Hybrid Synergy Drive is a technology developed and coined by Toyota which was originally revealed in the Prius models.


It appeared in the 2004 Prius as the second generation hybrid technology and is also being used in Camry, as well as in the Nissan Altima hybrid.


The term Hybrid Synergy Drive refers to the technology that powers the car. The main technology used in these hybrid cars is the Power Split Device which acts as a connector between the gasoline engine and the electric motor.

By default, the gas-powered engine is the primary source that exerts the maximum amount of power. It uses a regenerative braking mechanism that charges the battery every time you apply the brake and it utilizes the generated power to use the electric motor whenever needed.

Toyota created the HSD to create a hybrid car which is effective in making use of both the gasoline engine and the electric motor based on the charge available in the battery and the driving conditions.

To see how GM’s Chevy Volt works, read this article.

Parts of Toyota Hybrid Synergy Drive

A few different components are used together in order to get the Toyota HSD working as intended by the manufacturer, Toyota.

Let us take a look at the parts of HSD in detail.

Gas Engine – The Primary Component

While the gas engine is the primary component in any car for that matter, the Toyota hybrid car uses improved powertrains that are capable of exerting maximum efficiency with the help of modern technology. They are equipped with an Atkinson cycle engine that delivers a high expansion ratio and uses a four-cylinder technology to ensure the best efficiency for your ride.

Electric Motor

Owners of hybrid cars do know that there is an electric motor integrated into their cars. However, Toyota specializes in developing an AC synchronous-type motor.

They are powered by permanent neodymium magnets and the additional component is a rotor that is made using multiple electromagnetic steel plates arranged on top of one another.

The electric motor, even though not ideal for long drives, is capable of producing impressive output combined with higher drive torque.

Power Control Unit (PCU)

Power Control Unit may also be called the motherboard of your hybrid car.

The PCU is responsible for generating the maximum power from both the electric motor and the gasoline engine.

It also takes care of converting the direct current produced by the 12V battery in the car and deliver it as alternating current so that the electric motor would run.

The PCU is also responsible for providing increased voltage as it houses a high-voltage power circuit. The result allows the car manufacturer to have a compact inverter which saves space and has ample room for two different engines to be integrated into a hybrid vehicle such as the Toyota Prius.


High-Speed Generator

The generator is used to charge the battery and when the AC synchronous generator is operational at speeds up to 6,500 RPM or at times all the way up to 10,000 RPM, they deliver the required power. The power of the generator used in the model of the car you own will also determine the acceleration quality, especially when driving in low or medium speed. It helps maintain fuel efficiency by generating increased power as most people have to drive their car at low speeds during traffic conditions.

Planetary Gear – The Prominent One


Toyota Prius owners might easily recognize this component when it is referred to as the hybrid transaxle which acts as a bridge to transfer the power generated by the engine and the electric motor to the wheels. It is quite a complex setup that the manufacturers at Toyota have mastered through the decades they have been making Prius cars. The transaxle is directly linked to the engine and with the help of rotational shaft and pinion gears, it also establishes a connection with the motor and the wheels.


The setup is in such a way that the hybrid vehicle can be powered through multiple power sources and remain effectively operational.

If you want to watch a video for an introduction to Toyota Hybrid Synergy Drive, watch it below:


Which Toyota Models have Hybrid Synergy Drive (HSD)


According to Toyota’s official listing and considering the popularity of the hybrid models available in their line-up, these are the prominent cars that are powered by the Hybrid Synergy Drive (HSD) technology.

  • Toyota Prius
  • Toyota Prius C
  • Corolla Hybrid
  • Camry Hybrid
  • Prius Prime
  • Avalon Hybrid
  • RAV4 Hybrid
  • Highlander Hybrid
  • Lexus
  • Toyota Mirai
  • Toyota Yaris Hybrid


Being an owner of a hybrid vehicle, you would have experienced the unique build, performance delivered by these cars while maintaining better fuel efficiency and reducing emissions.

It is a great way to contribute towards a green planet while enjoying an amazing automobile driving experience.

What kind of problems to expect from HSD

Battery Issues

One of the most common problems that Toyota Prius and other hybrid car owners come across are battery issues that result in poor performance. Your car may have issues with the headlights, it may not start if you leave the car unused for several weeks altogether and it will also start malfunctioning if the same battery is used for years or thousands of miles without replacement.

Solution: An obvious solution to the problem is replacing the 12V battery used in the Toyota car which shouldn’t be an expensive replacement and will allow you to comfortably use the vehicle without any issues. Unlike other hybrid components, the availability of the battery is high and you should be able to easily find in your local store or online.

Inverter Malfunctioning

While this is not a ‘guaranteed’ component that will fail at a certain point, if your car has touched 100,000 miles or possibly somewhere around that range, some of the hybrid components including the inverter might fail. Replacing it with a new one would cost as much as $4000 and most users should consider buying a used one if you plan to keep using your hybrid vehicle.


Solution: If your car wouldn’t start or you face similar issues with your car, consider contacting a service center and get the DTC codes for the worn out components. Using the codes, you should be able to find a used version of the part within your own state or from a different place. In most cases, used components don’t come with a warranty or guarantee but they are much cheaper when compared to buying a new part for an old car.

Inconsistent Braking

The hybrid vehicle uses a regenerative braking system which allows the battery to be charged every time you apply the brakes. This particular technology is a mix of blended braking and friction braking, the latter used in conventional cars. Every time you apply the brake, the software is supposed to calculate multiple factors including battery’s charge level, speed, speed of the vehicle and steering wheel’s position to provide an optimal command to the braking unit. Such a complex setup has led to an inconsistent braking system which might intimidate you but it is an issue that is taken care of by Toyota in all the models released after 2010.

Expensive Replacement Parts and Non-Availability of Components

As years pass by, Prius and other hybrid car owners who possess vehicles that are really old, such as the 2004 model, may find it hard to find replacement parts if one of the hybrid components fails. Besides,
the newer cars released by Toyota after 2011 are much better in terms of reliability, technology and provide you the best Hybrid Synergy Drive has to offer.

It is one among the many problems that hybrid car owners face when they have to replace a part that may no longer be available in the used or new
market. At times, it could be very expensive that you might be looking to buy a new hybrid rather than spending too much on a car that is already 10+ years old.   


Owning a Toyota car which is powered by the company’s proprietary Hybrid Synergy Drive technology is an experience you can enjoy when you have a clear idea of how HSD works and the common problems that you might face. There are always solutions and checking out online forums, getting in touch with other long-time Prius owners will also help you solve a problem in case your car malfunctions.

There are other kinds of hybrids in the market today. Read this guide on PHEVS or this one on MHEVs. Its always useful to see the differences, and you can read about the differences between PHEV and regular hybrid here.

Hybrid Synergy Drive Animation

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