Why Prius Low 12 Volt Battery Car Won’t Start? How To Fix

When you note that the Prius low 12 volt battery car won’t start, you can feel worried and want to look for the best fix.

This problem often originates from various reasons, so you must determine the root cause to seek a suitable fixing method.

This article will thoroughly examine the most popular reasons for this Prius failure and the best way to solve it.

Besides, you can detect the potential breakdown in this automotive model through the evident symptoms. Also, we will tell you what will happen if this issue appears. Let’s read on!

Prius Low 12 Volt Battery Car Won’t Start: What Does It Mean?

prius low 12 volt battery car won't start
Prius Prime Low 12 Volt Battery

The Prius low 12 volt battery problem is when your vehicle battery is not charging properly. If the car’s battery voltage drops below 12 volts, it means that it is dead.

The low 12-volt battery indicates that your car is not getting enough voltage through the automotive battery to work. This problem can lead to serious failures.

What Are Signs of The Prius Low 12 Volt Battery Car Won’t Start?

The most common symptoms of a low 12-volt battery in a Prius include: poor start or stalling, dim lights, weak or failing radio system, error messages, unstable charge, or decreased fuel economy.

Poor Start

This is one of the most popular signs of a Prius low 12-volt battery vehicle not starting. Because of being a hybrid vehicle, Prius relies mainly on the battery.

Thus, it is hard to start when the dead or faulty battery can not have enough power. Or, it still provides sufficient battery power to crank up your car, but the start or power button does not respond.

Dim Light System

Another symptom of this problem is frantic lights. When you put your Prius in the ready mode, the exterior and interior lights are dim; it can warn that your battery is weak and needs a fix.

Radio Malfunction

Radio is a good indicator that tells you about a bad battery in your Prius. If the radio presets are lost since your vehicle gets started, you know there’s a problem with your battery.

Error Messages

When you notice a warning message from Prius’s dashboard about the battery, this part has gone wrong.

Thus, you should check the battery to determine the root and find the best fix to avoid battery damage and a negative impact on the engine’s performance.

Unstable Charge Level

Besides, if your car’s battery charge constantly fluctuates, your 12-volt battery is surely weak.

Fuel Economy Loss

If the car’s battery is weak, the internal combustion engine will be harder to function. This may lead to poor fuel economy and a clear symptom of a low 12-v battery in your Prius.

What Happens If Your Prius Has A Low 12 Volt Battery And Won’t Start?

toyota prius low 12 volt battery
Prius Has A Low 12 Volt Battery And Won’t Start Things Can Happen

Once a low 12-volt battery Prius doesn’t start, it will affect your car’s performance and other parts’ functions. If this problem happens for a long time, it will ruin your battery.

When the 12-volt battery becomes lower than the standard battery, it can produce excessive sulfation. 

This will build up the lead sulfate crystals on the battery’s lead plate surface, breaking the battery’s chemical balance and shortening the battery’s shelf life.

Low 12 Volt Battery Prius: What To Do?

If you’re stressed about driving with a low 12-volt battery, try a few ways below to solve the problem.

Recondition the Battery

You can recondition your car battery at home, and it’s fairly inexpensive. Reconditioning can extend the automotive battery’s life and is good to go when you’re trying to recover a weak 12-volt battery.

Clean Cells

One of the reasons your battery is running low is the cells capture the dirt. Thus, cleaning is a simple way to revive a low battery. Water and a baking soda mixture can clean the battery’s bad cells.

Charging the Battery

One of the easiest solutions is charging the battery when it gets low. Take the low battery out of your vehicle and charge it fully.

Replace the Dead Battery

The final method is to replace the low battery completely. This solution can be expensive, but it will help you save money and improve your fuel economy significantly in the long run.

If you can not repair the faulty battery, it is a must to replace it.

What Are Other Reasons Why Your Prius Won’t Start?

prius aux battery low won't start
Other Reasons Prius Won’t Start

Apart from a low 12 volt battery Prius, your car not starting can stem from various causes such as battery problems, ignition issues, blown fuse, clogged fuel filter, rodent damage, car engine failure, or poor key fob batteries.

Ignition Issues

This is one of the most popular issues that result in the Prius low 12-volt battery.

This failure is rooted from a defective spark plug that includes the spark to ignite the fuel mixture for the engine to generate power.

If the spark plugs are in trouble and stop working, your engine can not start.

Besides, if the ignition system’s plug connection loosens, your vehicle is also hard to start.

Thus, you need to check to find this cause and take your car to an automotive shop for the right fix or battery replacement.

Poor Key Fob Batteries

If your Prius can not be cranked up, its key fob battery might be weak. Once the automotive key fob battery runs out, pressing the button will no longer lock or unlock the door.

Don’t fret. This battery only signals you the unlocking or locking state, so you may still start your automobile with the start or push button.

Blown Fuse

In some cases, a blown fuse can also trigger the Prius to malfunction. Thus, you need to examine all fuses in the fuse box required to start the automotive engine.

Yet, be careful when you put your hand on the fuse box while it is operating. Take your car to the auto shop for a safety inspection and repair.

Fuel Issues

Fuel issues account for 5% (one in twentieth) of the reasons why your vehicle is not starting.

These include fuel pump issues and mechanical or electrical failures with the bad fuel system.

Battery Problems

Some battery problems such as dead batteries are the most common and serious culprits leading to the car not starting.

Besides the low 12V battery Prius, a failed battery can make the Prius engine not start due to the high battery voltage. Batteries produce high voltages exceeding 200 volts, which is a shock for your engine.

The dead 12V Toyota Prius battery is also another cause. The 12V battery helps keep the entire electrical system working even when parking.

If the dashboard light does not come on once you start your car, the 12V battery may die, or battery cables get corroded and lack the required current.

Clogged Fuel Filter

Another culprit behind this problem is the clogged fuel filter. Prius fuel filters don’t wear out like other automotive parts, but they can get clogged with particles in the air and dirt.

This failure will reduce the filter’s permeability and the fuel pressure accordingly. Plus, the engine may not start when the fuel filter becomes dirty.

Yet, you can not clean the dirty filter; replace it at an auto shop.

Fuel Pump Failure

The automatic engine will not start if the Prius’s fuel pump fails. The pump allows the required fuel amount to reach the engine’s injection system with sufficient pressure from the tank.

This problem can stem from clogged or worn pumps. You can check the leaks or the potential failure in the fuel pump.

It’s best to replace a bad fuel pump with the support of a professional mechanic at an auto shop.

Rodent Damage

Rodent damage is another reason why your Toyota Prius low 12 volt battery won’t start. Animals will crawl under your car and bite the wires or cables, such as booster cables.

This may harm the entire automotive system, such as electrical power, fuel, or engine oil supply. This damage is immediately apparent when you look into the automotive engine compartments.

Automotive Engine Failure

Despite being rare, this is also a recipe for the Prius malfunction. Nothing will work if your car engine gets damaged.

Typical causes of this problem are improper fueling, engine overheating, a malfunctioning timing chain, oil shortage, and continuous driving at excessive speeds.


The above are the main reasons why the Prius low 12 volt battery car won’t start.

These causes include poor key fob batteries, ignition or battery issues, fuel pump failure, rodent damage, automotive engine failure, or clogged fuel filter.

It is essential to check and identify the root of this problem. Also, you need to learn more about the common signs that help you detect a low 12-volt battery in your Prius.

When you know your Prius vehicle has a weak battery, you should find the proper solution to address it. You can use the useful fixes in this article to solve this problem without hassle.

Leave a Comment