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P0456 Diagnostic Trouble Code

Technical description

A small leak has been detected in the Evaporative Emission System.

What P0456 really means

The Evaporative Emission System is designed to prevent gasoline vapors from escaping into the atmosphere, and is built around a series of valves, rubber hoses, and a charcoal canister meant to collect vapors as they build up. These vapors are then systematically sent to the engine to be burned off. The computer regularly checks for leaks within this system, either by pumping in air, or by pulling a vacuum, and measuring the time it takes to reach a certain level. When a leak is detected the computer will command the check engine light on and set a P0440, which designates a problem in the system, and another code, such as P0455 0r P0456, to describe the size of leak or other problems in the system..

What causes a P0456 code?

It is good to remember that these leaks are small, in many cases small pinholes about .020”, and you should not worry about gasoline gushing out of the car. With the P0456, these small leaks are commonly seen on older cars, as rubber hoses and gaskets dry out. Most of this emission system sits underneath the car, so it’s exposed to a lot of the grime and wetness of the road during rough weather. Like it or not, these problems are unavoidable, therefore the best approach is to find a good mechanic

What is the severity of a P0456 code?

Minor. These size leaks should not make the car run poorly however, it will need to be resolved before an official emissions test.

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What repairs are needed to resolve a P0456 code?

A diagnostic check will be required to identify where the leakage is occurring. Because there is no noticeable change in how the car runs, many people will wait until just before an official emission or smog check. This may not be the best course of action, as this code usually will take some time to diagnose. Plan on dropping the car off for a whole day, and maybe more than one if parts are not readily available.

What is the estimated cost to resolve a P0456 code?

  • Estimated diagnostic cost: $100–$200
  • Estimated part(s) + labor cost: $50
  • Estimated total cost: $150–$200

The diagnosis might be the most expensive part of the bill. Unlike larger leaks, where components have failed or hoses have broken in half, small leaks are much harder to find. An initial diagnostic fee of $100 is customary with many shops charging an additional $100 if the leak is not found within an hour or if the components are difficult to access. Many times the repair is a new piece of hose, a rubber gasket between two components, or a new fuel cap, all of which will keep the repair portion of the bill under $50. However, there are cases where small leaks develop in the filler neck or even the gas tanks (the metal ones), which will bring repair costs up to the $500 to $600 dollar range.

Keep in mind, pricing will vary by location and your vehicle make and model. Save time and money by using Openbay to compare pricing and book an appointment with a service center in your area.

Service article written by an ASE Master Technician

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