check hybrid system

Uh oh. Does your Prius have a check hybrid system message on the dashboard? What does check hybrid system mean?

Many times, customers are upset when they call in to report this warning message. They’re assuming that the hybrid battery has failed, and that’s possible, but it’s not a foregone conclusion.

Here’s the good news. Just because the hybrid system warning light came on, it doesn’t necessarily mean you’ll need an expensive repair.

Sure, it might be a hybrid battery pack or inverter, but it might not, so don’t worry prematurely. There are many inexpensive issues that can cause the warning. There are even a few things you can fix yourself.

Check hybrid system displayed in green LEDs on a Toyota Prius dashboard.

So, what causes the check hybrid system warning?

So, what does the Toyota check hybrid system light mean? Most of the time the message indicates that the hybrid computer has found a problem with the hybrid system.

This system includes the transaxle (with electric motors), inverter, and hybrid battery. However, it doesn’t mean that any of those components have failed.

For instance, something as simple as a towel draped over the rear seat might cause the error message. There is a battery cooling inlet near the back seat. If it becomes blocked, it can cause the warning light.

It’s also possible that one of the hybrid system’s dependencies has a problem, like the internal combustion engine or ABS system. When this causes the message, it’s known as a “sympathy code” or “collateral code”.

Do you need to stop driving if the check hybrid system messages appears?

Let’s say a check hybrid system warning appears on your Toyota Camry. If you plan to keep driving, the most important thing is to look for other lights and indicators and to pay attention to any other issues with the way the car is driving.

Most of what you worry about

Many years ago, I got hired at Contra Costa College to teach hybrid repair. When I went to HR to do the paperwork, they asked for my master’s degree.

“Um, no master’s”, I said.
“AS degree”?

I had to enroll and finish a degree and PE was a requirement.

Great, an old guy in a college PE class, I thought.

As it turned out, I loved the PE class, which was run by the legendary Coach Creer. I continued on with the class for years after my degree was complete.

One of the things he used to say was “90% of the things people worry about never happen”.

For instance, if you also see a red thermometer with wavey lines under it, your car is overheating. Stop driving right away and call a tow truck. The same goes for the low oil pressure light.

A couple of examples

Let’s say you own a 2009 Toyota Highlander Hybrid, and the check hybrid system warning appears. The car seems to be driving fine so you drive it in.

When it gets here, we find a P0AA6 caused by a water leak. The car hasn’t been hurt at all. It was fine to keep driving.

But here’s another scenario. Let’s say you have a Lexus CT200h, and the check hybrid system warning appears. The car seems to be driving fine and you need to get to work. However, you didn’t notice the small icon on the multi-display indicating overheating.

Unfortunately, the electric water pump fails on this model. It has the same engine as the 2010-2015 Toyota Prius, which is known for head gasket failures. A failed water pump can lead to a very expensive repair. This is a car you would want to tow in.

What should you do? It’s always safe to tow the car so that’s what we recommend.

How to reset check hybrid system

Unfortunately, the warning shouldn’t really be reset. To be clear, you can reset the check hybrid system warning, but you shouldn’t.

So why not reset it? Here’s the main reason:

When the check hybrid system alert appears, diagnostic data is stored in the control unit. This data is what we use to diagnose the problem with your car.

If you erase it, we’ll need to recreate the problem before we can start to find out why the warning appeared. This will take time and cost you money.

However, there are some valid reasons to reset the check hybrid system warning. Some codes, like loss of isolation codes, will prevent the car from restarting. If you need to move the car out of a parking garage or something, it might make sense to clear the trouble codes.

So, how do you reset it? There are two ways. Either use a scan tool to clear the diagnostic data, pull the backup power fuse for the ECU, or simply disconnect the 12V battery and wait a while before reconnecting it.