You can find information about the P0456 fault code on this page.
It is one of the most popular fault codes that people search for on this website (in the top 50).
We have given it a seriousness of 3/10 with 1 being the least serious and 10 being the worst.
Looking To Fix This Yourself?
By using a workshop/repair manual you could diagnose and even fix this issue yourself.
You can find a collection of free manuals containing loads of information specific to your car on our partner site.View Workshop/Repair/Service Manuals »
The fault code P0456 is logged as a result of a very small leak being detected in the evaporative emission control system (EVAP).
The EVAP is a closed system in the vehicle with the sole purpose of preventing excess fuel vapors from leaving the fuel tank and entering the surrounding atmosphere.
This code does not indicate that there is a fuel leak, only that there is a very small vapor leak in the closed EVAP system. These can be extremely small leaks.
These systems became a requirement for all vehicles around 1970.
This means that nearly every car on the road today will have one of these systems, meaning any can suffer this fault code. However, some of the most common brands to have this issue include Audi, BMW, Ford, and Nissan.
Other Signs of This Problem
Any issue with a vehicle’s EVAP system comes with notoriously few indications (aside from the P0456 fault code). The most noticeable issue is the presence of the Check Engine light. An OBD-II test is the best way to determine the nature of the fault.
In rare cases, a smell of fuel can be detected if the vehicle is parked in a confined space like a garage. However, this is more likely with code P0455, which represents a large leak in the EVAP system.
What Could Be The Problem?
There are relatively few components in the EVAP system, but fault finding can still be very difficult.
However, one of the main causes of these types of errors is an issue with the gas cap. If the fuel cap is not tightened properly, it can allow for a leak that triggers this or other similar codes.
A faulty or damaged gas cap can also prevent a correct seal from being formed, again, allowing a leak to be detected – leading to the P0456 fault code.
There could also be damage in one of the components like the purge valve, wiring, or fuel lines.
Fixes are most focused on finding the source of the leak and rectifying it. This can be as simple as adjusting the gas cap or replacing damaged parts.
The gas cap is by far the easiest component to adjust in this instance. Be sure it is a factory gas cap with no faults and that it is always tightened fully before running the vehicle.
In some instances, it will take a few times running the vehicle before it can remove this fault as a result of a loose gas cap.
Look for leaks in the fuel lines and components. In the case of P0456, these can be extremely small in size, so be sure to be extremely thorough. A specialist diagnostic tool called a ‘smoke machine’ is typically used to find these leaks.
Check the wiring and connections for any damage that would cause a poor reading to be registered.
Issues with the EVAP system are almost low in terms of seriousness. There is no risk presented to the occupants of the vehicle or the vehicle itself through normal operation. It is fine to fix this issue within a few weeks.
Be aware, if you are subject to an emissions test for whatever reason with this P0456 code, there is a chance your vehicle will not comply with regulations. This will likely result in a fine.
Popular Fault Codes
These are the most popular fault codes that people are searching for.
Intake Camshaft Position Actuator Circuit / Open (Bank 1)Read about code...
Intake Camshaft Position Timing - Over-Advanced (Bank 1)Read about code...
Intake Camshaft Position Timing - Over-Retarded (Bank 1)Read about code...
Exhaust Camshaft Position Actuator Circuit / Open (Bank 1)Read about code...
Exhaust Camshaft Position Timing - Over-Advanced (Bank 1)Read about code...
Crankshaft Position Camshaft Position Correlation Bank 1 Sensor ARead about code...