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P0456 is a diagnostic trouble code (DTC) for "Evaporative Emissions System Small Leak Detected". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
Evaporative Emissions System Small Leak Detected
P0456 is an OBD-II generic code that the engine control module (ECM) has detected a very small leak in the evaporative system during the vehicle off testing. The test has to fail twice in a row to cause the code to be activated by the ECM.
The ECM has commanded the purge control valve to close the system and activates the evaporative vacuum pump to bring the system into a small amount of specified vacuum and then monitors the system for leaks. If the system detects a very small leak during the test then the ECM stores the code and waits till a second test can be done and if that test detects a very small leak then the ECM stores the code P0456 and turns on the check engine light.
The cause of code P0456 can be a small leak at any of the system components or hose connections.
The two most common causes of the code is the gas cap vent and the purge vent valve will not seal completely.
The Check Engine Light will be illuminated and the code is set in ECM memory.
Scans codes and documents the code in the ECM, views the freeze frame data to see when fault happened
Inspects the entire vapor purge valve system to include the purge valve and vent valve hose connectors for damaged or loose connections
Checks the purge valve vent for any blockage from dirt, debris or spider webs that could cause the valve to not be able to complete a total seal of the vapors
Performs a smoke leakage test on the fuel vapor system to try and locate the cause of the vapor leak using the test vapor port, checks the fuel cap for vent leakage
Checks the purge control valve to see if it will hold a vacuum when activated
Not checking and assuming the purge control valve is defective without doing a thorough diagnostics of the complete system to later find the wiring is broken or cut
Not verifying the leak and replacing parts that may or may not be the problem
Not checking for any technical service bulletins that may have a fix for the code
Code P0456 causes the Check Engine Light to go on and this alone will cause a failed emission test.
The code means the fuel vapor system has a very small leak and may be hard to locate on some vehicles and the code will keep coming back till the leak is found.
The ECM monitors will not pass emissions if the leak is not found and just the Check Engine Light is turned off.
Code P0456 is not a common code for most vehicles and some manufacturers do not use the code at all. Vehicles that come in with the Check Engine Light on with this code the most common cause is the fuel cap or the purge control valve or the vent valve will not hold in the vapors completely and have very small leaks that are detected.
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