How to Test the Hybrid System on a Prius

If the “Test Hybrid System” indicator lights up on the dashboard, it means that the Prius has a problem with the engine or electrical system, or simply a minor fault. There are many reasons why this light is on, and the remedy depends on the specific cause. We’ve answered some frequently asked questions about testing hybrid systems in Prius vehicles to help you fully understand the problem and find the best solution.

Table of Contents

What is the purpose of the hybrid system test light?

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This light illuminates when there is a problem with the vehicle’s hybrid system. The Prius is equipped with a hybrid system consisting of a battery-powered electric motor and a gasoline-powered internal combustion engine, the two working together. When the “Check Hybrid System” light comes on, it means that the vehicle’s warning system has detected a problem. It could be something as minor as a broken fuse, or something more serious like a faulty alternator. ^{[1] X Research Source}

Sometimes, the system says there is an error when there is really no error. If this is the case, you just need to restart the car and the error will be gone.

Can I drive with the hybrid system check light on?

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You should not ignore this warning light. Although you can still drive when the indicator light is on, damage to the vehicle can become more serious. If the light does not go out after you have restarted the vehicle, you should call an ambulance or drive yourself to the repair shop as soon as possible. If there is a problem with the vehicle, finding it early will save time and money in the long run. ^{[2] X Research Source}

How do I remove the hybrid system test message?

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Pull over to the side of the road and turn off the engine for a few minutes to clear the error message. If the hybrid indicator light comes on while the vehicle is moving, you should steer the vehicle to the side of the road. Turn off the engine and wait 5-10 minutes. Then reboot to clear the error message. If the light doesn’t come on then it could be a system fault and nothing is wrong with the vehicle. However, if the lights are still on, the car may have a problem. ^{[3] X Research Sources}

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Check the fuse as that could be the cause. If the hybrid check light remains on after you’ve restarted the vehicle, look for a blown fuse. Check under the bonnet or dashboard for the fuse box. Look for small fibers or discoloration. Replace the burned fuse with a new fuse of the same type and see if that fixes the problem. ^{[4] X Research Sources}

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Take the car to the repair shop and have them scan the code. If you cannot find the cause of the fault on your vehicle, have it checked by a mechanic. They can connect the device to the vehicle’s computer and scan the system for errors. ^{[5] X Research Sources}

How to test the hybrid battery of a Prius?

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Plug the OBD2 adapter into the vehicle. The OBD2 adapter is specially designed to read the Prius’ computer system and let you know if there is a problem with the battery. ^{[6] X Research Source} Remove the small cover under the dashboard to the right side of the steering wheel to access the connection port. Then plug the adapter into this port. ^{[7] X Research Sources}

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Use the Dr Prius app to check battery health. Go to the app store on your smartphone or tablet to download the Dr. Prius. Connect this app to OBD2 device via bluetooth or wifi. ^{[8] X Research Source} Then check the application to see if the OBD2 adapter reports a battery error. ^{[9] X Research Source}

If the battery is in good condition, the problem may lie elsewhere.
Take your vehicle to a repair shop if there is a problem with the battery.

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Take the car to the auto dealer or mechanic for added convenience. If the car is still running, bring the car to a repair shop to have them check the system for battery problems. ^{[10] X Research Source} If the car can’t run, you can call a mechanic to have them come and check the car’s battery.

Diagnostic testing usually costs about $120 in the US.

Why can’t the Prius start?

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The cause is usually in the generator, starter, or battery. These are the most common reasons why your Prius won’t start. The repair can be done by replacing, cleaning the connection, or repairing. Since there are many potential causes, it is important that you bring your vehicle to a repair shop for a comprehensive diagnosis. ^{[11] X Research Source}

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You may have over-oiled the engine. The user manual is very helpful and shows what type of oil the car uses. But because the Prius is very sensitive to engine oil, if you add too much, it won’t start. It is a measure to prevent the car engine from being damaged. If the car has no problems, the cause may be engine oil. Try draining the oil and refilling it or have a mechanic change the engine oil. ^{[12] X Research Source}

Is my Prius subject to a recall?

Advice

If you are not sure what to do with the hybrid system check light, contact your dealer for assistance.

Warning

Do not ignore the hybrid system warning light. This can cause more serious damage and require more expensive repairs.

Steps