Prius Won't Turn Off - Unexpected Reasons and Solutions for the Issue

Nobody wants to get stuck inside a vehicle with a motor on and be unable to turn the engine off. It sure is one of the unluckiest times when you, finally, are about to rest after a long or short drive from work. But then, you find it unable to leave your vehicle because the engine won't shut off. 

You have no idea, but risks come along with having a continuously running hybrid engine that doesn't want to stop. It could drain your battery and consume all the fuel while it waits to shut down properly.

Another risk you'd like to avoid when you cannot turn your engine off is the tendency of your vehicle to move away when it is still running. It can cause potential accidents, and the only way to move out of the situation is to address the issue as soon as possible.

For this reason, we summarized the possible reasons why your Prius don't shut down and how to fix it.

Reasons why Prius Won't Turn Off

1) Defective Combination Meter or Instrument Cluster

In most cases, Prius does not turn off because of a faulty combination meter or instrument cluster. 

The combination meter is a set of gauges that displays significant driving information such as fuel level, speed rate, and gear. 

In 2019, there was a recall for 2019 Prius units due to combination meters. According to the investigation, the combination meter had short circuits in the gauges, including the speedometer, odometer, and fuel gauges. These electrical issues cause the entire device to go blank. 

In these cases, the engine is still running and would not shut down. If the problem is in the combination meter, you will notice the following symptoms:

• Blacked out dashboard
• Locked rear hatch
• The engine doesn't turn off

The probable reasons why combination meter gets defective are damaged or corroded cables, internal components failure, loose connections, improper installations, and damaged sensors. 

In any case, the only fix for this problem is to replace the combination meter. However, you need to shut off the engine, and we will provide you with a quick way to shut the engine. Toyota has set this safety override. You only have to press the Power button for about three seconds, and the engine should shut off.

However, in some cases, the infotainment still runs. You only have to tap the power button twice quickly, and it should disconnect all the electronics. By this time, you can now get off your car and lock it in place.

2) Battery Problems

Battery issues can cause the engine to prevent from shutting off. Here's why:

• Dead High-voltage Battery

A dead high-voltage battery can cause the engine not to turn off. The high-voltage battery of the Prius vehicle supplies power to its electrical components. If your Prius HV battery becomes drained, it will not provide enough electricity to run the vehicle or power up electrical components. 

However, the engine would still run because Prius is a hybrid vehicle that would run in fuel-only mode. Components relying on electric-only may not function smoothly or not work at all.

When turning off the engine, the system sends the signal for the engine to shut off. However, it needs electric power for sensors to send information and the ECU to read the received information. With a dead HV battery, the car's ECU may not receive the signal to shut the engine off, and the sensors may not transmit the data to the computer.

There are many reasons why an HV battery dies: 

• Age
• Not used for a long time
• Overuse
• Extreme temperature
• Defective cells

In these cases, replacing the high-voltage battery is your best fix. Some people extend the life of their HV battery through reconditioning, but this fixing method may only extend the battery life for a short time. Also, you can not utilize regenerative braking efficiently when the HV battery is dead.

• Dead 12-V battery

A dead 12V battery can damage to electronics in your car and prevent the Prius computer from receiving signals to shut the engine off. In most cases, it could blow fuses, damage sensors, or short circuits that may prevent the engine from shutting down.

Aside from age, there are more reasons the 12V drains prematurely. Sometimes, you do not notice, but leaving the engine in park mode drains the 12V battery. Also, some other electrical components can consume power from the battery even if the device is off. Some examples of these components are stereos and car alarms. Also, a defective alternator will not generate new power to charge the battery. So, it may drain over time.

To handle this situation, remove the battery, charge it, or replace it. If charging still works, do not forget to check if certain components have been drawing power and causing the battery to drain faster, even if those devices are off. 

3) Electrical Issues

Many electrical issues could cause your Toyota Prius not to shut off. Since it runs on hybrid technology and mostly on electricity, components can wear off or malfunction before they send the signal to turn off to the ECU. 

A common issue for Prius is a bad ground connection. Bad ground connections prevent the continuous supply of electricity to electrical components, including the ECU. It results in many electrical problems, such as short circuits and damage to devices like the combination meter. Bad ground affects wire connections, fuses, relays, and sensors. 

If this happens, it may interrupt the communication between the ignition and engine, which both relies on a continuous electrical supply. This instance will prevent the vehicle from turning off properly.

4) Shift Cable Problems

Shift cable problems may indirectly cause your engine not to turn off. When shutting off a Prius, you need to shift your gear to Park mode before turning off the engine. However, if your shift cable becomes bent, misaligned, or broken, your gear will remain in Drive mode. 

These problems arise from continuous usage, where the cable overstretches or jams into the assembly, preventing it from shifting into park mode. Some shifters move to the park position but don't move out of drive mode.

Some Prius owners try their luck jiggling the shifter until it finally switches to park mode. However, this method does not usually work. And you still need to pry off the cover to fix the shifter or replace it. 

5) Security Problems

The Prius security system usually prevents unauthorized access from starting the engine but not shutting it off. However, some instances may indirectly cause the motor not to turn off. These cases are most likely related to malfunctioning keyfob or ECU not receiving proper signals to shut off. 

If the system does not recognize the keyfob, although keyfobs are not required to shut off the engine, it can cause miscommunication between the ECU and the keyless entry. It could trigger incorrect error messages or interfere with signals to shut off the engine.

6) Defective power button

The power button is responsible for starting your engine and turning it off. If this component is faulty, it may not send the signal to shut off. 

Mechanical defects can affect the performance of the power button. Some defects could be in the button itself, the connections, or the sensors that detect the input from the button. In any way, these defects could prevent it from sending the signal to the computer.

The power button can accumulate dirt and grime, which may affect the connections with the button. You can try cleaning the sides of the button and ensure that it doesn't get exposed to moisture.

If it's not responding, it's probably because of a dying keyfob battery. Try changing your keyfob battery with a new one.  

If the power button needs replacement, the only way to solve this is to bring it to your service repair shop.

How Can You Turn Off Prius That Doesn't Shut Down?

Solution 1 Press the Power Button

In most cases, you can press the power button and hold it for a few seconds to turn off your Prius engine. 

First, find a slot for a smart key in your dashboard. Insert the Prius smart key. Push the power button and hold it for a few seconds. Release the button and remove the smart key.

This method should reset your system.

Solution 2 Replace your Instrument Cluster

The common reason your Prius doesn't shut down is a defective combination meter. Some people turn their lights on and off thrice while pressing the information button when their Prius do not turn off or the dashboard blacks out. However, most reports we received say the problem is recurring. 

The problem keeps coming back because they did not replace the instrument cluster yet. If holding the power button does not fix it, it's probably in your instrument cluster. 

You have to address it at once because your battery will drain. Our best recommendation is to bring it to your trusted technician for accurate diagnostics. 

Final Thoughts

Now that you understand the probable reasons Prius won't shut off, it's time to find out what happened to yours. If your gauges blacked out, you'd probably need to replace your combination meter. 

Even if your Prius has been showing early signs of irregularities when turning it off, address it sooner so you will never experience getting stuck in the middle of a ride with your engine on.