Prius P Lock Malfunction (Solved & Explained)

The P lock malfunction will randomly appear and prevent the Prius from turning on all the way. You won’t be able to shift your Prius vehicle out of park. Battery issues and fuse issues are usually the primary cause of p lock malfunction.

What causes Prius p lock to malfunction 

Shifting our vehicles into Park is something that we do several times a day. We barely even think about it as we shift the gear into park, turn off the vehicle, take off our seatbelts, and open and close the door.

But there are some issues that can cause the Prius to lock our vehicles into the park gear. When it is locked in the park gear, the driver cannot shift it out of park and into drive or reverse or neutral. 

When your vehicle warns you of the p lock malfunction, it will say:

P lock malfunction. When parking, park in a flat place and apply the parking brake securely.

You’ll pretty much be stranded wherever you parked until you can figure out how to unlock your vehicle. Some people have come back to their cars, turned on their Priuses, and discovered the pillock malfunction warning. 

They did not know it was coming and now they’ll have to scour the internet to understand what’s going on. Hopefully, you never get locked out of your vehicle via the P lock malfunction.

So what would cause the Prius P lock to malfunction?

An accident drained the battery

We’ve all accidentally drained our vehicle’s batteries. Perhaps he left the lights on overnight. Maybe the driver-side door was open for too long. 

But whatever the reason, you will need to find a way to charge up the battery just enough so that you can drive your Prius around and its internal mechanisms can charge the battery. 

Find someone who can help you jump-start your vehicle. Just because your battery drained doesn’t mean that the battery is faulty or needs replacing. 

A faulty fuse in the fuse box

There is a fuse in a fuse box that controls the Prius’s parking system as well as the inverter and converter. When this fuse blows, the P lock malfunction will return until you or a mechanic replaces the fuse. 

It is not always known why this fuse burns out, but it is a fairly easy replacement. A box of fuses does not cost more than $20. If you can use your driver’s manual to locate the correct fuse, you can replace it yourself. 

You won’t need to go to a mechanic. But replacing the fuse is only temporary. If you don’t find out the reason why the fuse blew out in the first place, it will blow again.

A faulty 12-volt start or auxiliary battery 

The auxiliary battery, or 12-volt battery, is the main battery component for turning on the engine and making sure all the components in the startup process work correctly and have power. 

If there is an issue with the 12-volt starter, it is simple to detect if you have the right tools. Mechanics can easily test the starter or the battery and see if it is working correctly. Since it is not, you will need to replace the 12-volt starter battery.

The average price of a 12-volt starter battery or auxiliary battery can be up to $350 just for the battery. The Battery Plus the labor to replace the old malfunctioning battery can be expensive as $500.

How to fix a P lock malfunction

So you came back to your vehicle, turned it on, and discovered the P lock warning light. Well, you don’t want to sit in the parking lot or side of the road for a few hours. You have to get home, so how do you solve a p lock malfunction?

The brake pedal pump fix

First, try to turn on your vehicle. It might not turn on all the way to where the engine revs. But make sure the dashboard is lit up. 

Then, press down hard on the brake pedal several times. Now, turn on the ignition again. If it worked correctly, then the Prius will turn on all the way and you’ll hear the engine turn on as well. 

If this does not work, turn the vehicle off completely, wait a minute or two, and then try again.

Disconnect the battery fix

If you’re at home when the P lock malfunction warning light appears, you can disconnect the battery. Here’s what you need to do. 

First, open the hood of your Prius and then turn your vehicle off completely. Put on a pair of heavy gloves. 

Now, disconnect the main cable from the battery. If you do not know what the cable looks like, you can use your owner’s manual. Also, check online for a visual guide on how to disconnect a Prius battery. 

Once you disconnect your Prius battery, wait a few minutes. 

Then, reconnect the cable to the battery. Make sure it is and its exact original position. Now turn on your vehicle again. 

You may see several warning lights as the vehicle warms up and charges. But the P lock malfunction warning should not appear.

Until you get the issue fixed, the p lock will continue to turn on randomly.

Be prepared to call a tow truck

The brake pedal fix and the battery disconnects will not always work. Since the p lock is malfunctioning, ‌ take your vehicle to a mechanic to learn why it is malfunctioning. 

Some Prius owners go looking for answers in Prius Forums. But they’re unable to find answers and they have to call a tow truck to take their vehicle to a mechanic.

Conclusion

A drained battery, a faulty battery, and a burnt-out fuse will trigger the Prius’ P lock to activate. There are ways to fix the p lock temporarily and unlock it so that you can drive home. 

You can disconnect the battery or you can pump the brake pedal several times while the vehicle is on standby. But these fixes don’t always work and you may have to call a tow truck to take your vehicle home and to a Toyota mechanic.