Diagnostic Trouble Codes (DTCs) are never fun to look for, but unfortunately, your vehicle sometimes leaves you with no other choice. If the Check Engine Light is on and the OBD-II scanner reads the P0456 code, it’s good to familiarize yourself with some basic facts about this DTC, as well as the ways that you or your mechanic can diagnose and repair it.
The meaning and cause of the P0456 code
Let’s get started with the basics: there are two main DTCs, generic and manufacturer-specific. Generic codes, also known as SAE, apply to all OBD-II equipped vehicles and are fairly easy to find online. Manufacturer-specific codes, on the other hand, are more difficult to find online, as not all manufacturers are willing to share their information. Fortunately, the P0456 code is a generic powertrain code, which means it applies to all OBD-II equipped vehicles. However, even with generic codes, the specific diagnostic and repair steps may vary from model to model.
But what does the P0456 code mean?
To put it simply and bluntly, this is a code for “evaporative emissions system – small leak detected”. In other words, when the scan tool reads the P0456 code, your OBD-II system has detected a lack of pressure at the Fuel Tank Pressure (FTP for short) sensor within the Evaporative Emissions Control System (EVAP for short). abbreviate), indicating a small leak. By the way, your Check Engine Light will not come on if a leak is detected only once; the test for this leak must fail twice in a row for that light to start to shine.
What causes the P0456 code?
As usual, things are never black or white with DTCs, which means that there may be quite a few causes for the code. However, this particular code is easier to understand than, say, the P0303 code. This is because the P0456 code is detected in a very specific way. So, to understand the possible causes, you must first understand the process behind detecting the P0456 code. Fortunately, we made this process super simple for you:
- The Powertrain Control Module, or PCM for short, signals the purge control valve to shut down the system and turn on the evaporative vacuum pump so that the system can enter a vacuum state. Why is this being done, you ask? So the PCM can test the system for leaks.
- If the system detects a loss of vacuum pressure during the test, the PCM stores the code and waits until a second test is performed. Remember how we said your Check Engine Light won’t start to glow until the leak test fails two times in a row? So now if the second test detects the leak again, the engine control module will store the P0456 code and activate the Check Engine Light.
Because the leak usually occurs within system components or hose connections, the most common causes are:
- Purge vent valve and / or gas cap vent is not sealing properly
- Leaking or disconnected EVAP hose
- Leaking fuel tank
- Damaged canister vent valve
- Leaky Coal Canister
Symptoms of the P0456 code
Because the EVAP is a closed system, drivers generally don’t notice any symptoms other than the glow of the Check Engine Light. This occurs because the EVAP does not control the management of the engine, only the vapors from the fuel tank.
With that said, this is what most drivers will notice:
- Check Engine Light is on (always occurs)
- Smell of fuel (not that common)
- Decreased fuel consumption (not that common)
Diagnosing and repairing the P0456 code
To properly diagnose a DTC, a thorough inspection of the vehicle is necessary. While you can perform some of the diagnostic steps yourself, it is recommended that you take your car to a professional, unless it is one. This is advisable because errors are common with the P0456 code. EVAP components are often replaced by mistake when there is a vacuum leak or the fuel cap is not tight.
In either case, a mechanic will:
- Connect the …