Cause and Fix for P0456 Code Toyota

The common causes of P0456 engine code are an open gas cap, broken EVAP line, gasoline tank leak, and a defective purge valve and damaged vent valve or charcoal canister. The Solutions for the causes are tightening the gas cap, repairing the EVAP line, fixing the gasoline tank, and replacing defective or damaged purge valve, vent valve, or charcoal canister.

The P0456 engine code is a diagnostic code that specifies a small leak in the EVAP system in a vehicle. I have discussed all possible causes of the P0456 engine code and how to solve them.

What Is Po456 Code

Engine code is a set of codes stored in the ECM of a vehicle. The P0456 engine code means that the ECM in your vehicle has recognized a small leak in the EVAP (Evaporative Emission Control System) system.

As a result, your vehicle may run out of fuel faster and cover less distance.

When your vehicle has the p0456 code in the scanner, the exhaust system releases harmful pollutants into the environment. Apart from this, there is no major issue with this code.

3 Symptoms of Po456 Code

The P0456 code does not indicate any major problems, but there are 3 main symptoms of the code.

  1. You see the Engine Light on.
  2. Either inside or outside the car, you can smell fuel.
  3. Your vehicle gets less MPG.

Po456 Code Toyota | 4 Causes and Solutions

P0456 engine code has 4 primary causes. I have covered all the causes and solutions, in general, to help you understand the code clearly.

Cause 1: Open Gas Cap

The Gas cap covers the gasoline tank to prevent vapors from escaping and external dust from entering the tank.

If the gas cap is unattached or loose somehow, the vapor comes out of the fuel tank and causes the P0456 code.

Solution: Follow these 4 steps to replace the gas gap.

  1. Turn the gas cap and set it in place tightly.
  2. Clean the gasket with a wet cloth.
  3. Examine the filler neck for damage.
  4. Replace the gas cap if it is damaged.

Cause 2: Broken EVAP Line

Charcoal Canister works as a gasoline vapor storage device. EVAP Lines link gasoline tank with charcoal canister.

If the line is broken, the vaporized fuel leaks out.

Solution: Check the EVAP line. If it is broken or damaged, repair it. The better solution is changing the hose. You may use a smoke machine to check the line.

Cause 3: Gasoline Tank Leak

The gasoline tank stores fuel for a vehicle’s engine. It also prevents gasoline vapors from leaking out. If there is a leak in the gasoline tank, it allows the vaporized fuel to come out.

Solution: Observe the gasoline tank for any holes or leaks. If you find any leak, repair it. Welding is the best solution to the problem.

You may also consider Rubber Sealant or Epoxy Putty to repair the tank. If the leak is beyond repair, replace the tank.

Cause 4: Defective Purge Valve

The purge valve controls gasoline vapors from the EVAP canister to the engine’s intake manifold.

A defective purge valve fails to purge vaporized fuel into the engine, enabling gasoline vapors to enter the air.

Solution: You will find the purge valve on the right side of the air box. Observe the purge valve and make sure it is not stuck open or closed.

Clean the valve if possible. If it is fully damaged, replace it.

Other Possible Causes for the Po456 Engine Code

I have already covered all the significant causes of the P0456 code. The code has a few less serious causes as well, though.

2 other factors can also be the cause of a small EVAP leak:

  1. Damaged Vent Valve or Charcoal Canister allows the fumes to enter the environment.
  2. If the EVAP system components are not installed correctly, it can cause the P0456 engine code.

Examine each of the factors in detail. Repair or replace the parts as necessary if you find any damage.

How to Diagnose P0456

To identify the P0456 engine code, use an OBD-II Scanner tool. To troubleshoot, look for all P0456 symptoms that match.

I advise contacting a professional technician to troubleshoot and resolve the problem if you lack the confidence to diagnose and perform further steps.

Is P0456 Serious

Your vehicle will be impacted as follows if it has the p0456 code:

  1. You will see the vehicle has less engine power.
  2. To drive the same distance, it will burn more fuel.
  3. You will feel vibrations when you start the engine.
  4. The exhaust system will emit many pollutants into the air.

Though the P0456 engine code has no harmful effect, it reduces the Odometer reading in the long run.

How to Prevent P0456 Engine Code in the Future

Follow these 3 steps to prevent the P0456 code in the future:

  1. Check the gas caps every 4000 miles (6,400 km).
  2. Examine the EVAP system in your vehicle every 7500 miles (12,070 km).
  3. Clean the fuel tank every 3–4 months and check for leaks.

P0456 Code Repair Cost

The cost of fixing the P0456 error code will vary depending on the parts and your location. I have provided a table to help you understand the estimated cost of fixing the P0456 code.

Depending on your location, a technician will cost you between $100 and $200 in addition to the parts.

Parts Cost
Gas Cap $5-$20
EVAP hose  $10-$50
Purge valve $20-$50
Charcoal Canister $50-$100
Vent Valve $5-$50


Does p0456 clear itself?

Yes, the P0456 code can clear itself when the leak is repaired. But the code doesn’t clear immediately after the repair. You may need to drive the car a short distance or reprogram the ECM to clear the code.

Can I drive with a p0456 code?

Yes, a loose gas cap can cause a P0456 code. The gas cap prevents gasoline vapors from leaking out. If the gas cap is loose, gasoline vapors leak out, causing the P0456 code.

What happens if you continue to drive with a P0456?

If you continue to drive with a P0456 code, your vehicle may not have any major issues. But there are still some things that need fixing.

Your vehicle may have less engine power and decreased fuel economy.

You will feel vibrations when starting the engine, and the exhaust system will discharge more pollutants into the air. Overall, your vehicle will get less MPG.

How do I clear permanent code P0456?

You can clear permanent code P0456 by using an OBD-II scanner. But the scanner will show the code again if the issue is not repaired properly.

So, you have to solve the problem correctly first.

What is rough idle P0456?

Rough idle (P0456) means your vehicle does not run smoothly when it is idle.

P0456 is an engine code that indicates there is a problem in the EVAP system of your vehicle.

Among the problems, your vehicle may have a rough idle. You can diagnose the issue with an OBD-II scanner tool.

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