The P0455 diagnostic trouble code appears when there’s a leak in the Evaporative Emission Control (EVAP) system, and the system can’t maintain pressure.
The EVAP system usually consists of five main components: the fuel tank, fuel cap, vent valve, purge valve, and evaporative canister (or charcoal canister).
The purpose of the EVAP system is to prevent fuel vapors from escaping into the atmosphere. According to some sources, around 20% of all vehicle-produced air pollution originates from vehicle fuel storage.
The engine control module (ECM), therefore, will perform leak tests from time to time to make sure all parts of this system are in working order.
To do this, certain parameters must be in place. To test while parked, the vehicle and ambient temperature will be within range of each other, testing to see if fuel vapor can escape while not running.
There are also tests while running. The ECM will cycle the vent control valve and purge valve to create a sealed EVAP system. In turn, the EVAP system will signal a large leak if the system can’t maintain pressure.
What Does the P0455 Code Mean?
Diagnostic trouble code (DTC) P0455 stands for “Evaporative Emission Control System (EVAP) Large Leak Detected”. Your car’s computer will set the code when it determines there’s a significant leak in the EVAP system.
Users have reported code P0455 for the following makes: Chevrolet (especially on a Chevy Silverado), Dodge, Ford, Jeep, and Nissan.
P0455 on Some Chevrolet Vehicles
Code P0455 may appear on some Chevy vehicles. On a 2010 Chevrolet Silverado 1500 LS 5.3L V8, for example, this DTC is set when “the EVAP system is not able to achieve or maintain a calibrated level of vacuum within a set amount of time.”
The code appears in a 2010 Chevrolet Silverado 1500 5.3L V8 because of the following conditions:
- The ignition voltage is between 11–32 volts.
- The barometric pressure (BARO) is more than 70 kPa.
- The fuel level is between 10–90 percent.
- The engine coolant temperature (ECT) is less than 35°C (95°F).
- The intake air temperature (IAT) is between 4–30°C (39–86°F).
- DTC P0455 runs once per cold start when the above conditions are met.
For the circuit/system testing of Chevy vehicles, it’s important to note that larger volume fuel tanks and/or those with lower fuel levels may require several minutes for the floating indicator to stabilize.
Note: The definition of trouble code P0455 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.
What Are Some Causes of a P0455 Code?
Numerous factors might cause the leak. Most often, the leak has something to do with the fuel filler cap. It could be missing, not sealed properly, damaged, or not correctly installed. Sometimes, the P0455 code can be set while fueling incorrectly or even by failing to turn off the engine while fueling your vehicle.
Another common cause of this code triggering is leaks. Hoses (like the large one connecting the filler neck to the tank) can crack with time.
The EVAP system’s purge valve is used to regulate pressure and is one of the things you should check first when you get the P0455 code. A visual inspection of readily viewable components is an efficient first step.
More possibilities include:
- Aftermarket EVAP hardware that doesn’t conform to the EVAP return tube
- The EVAP purge valve is stuck closed
- A slow-responding EVAP purge valve
- Blockages in the fuel vapor hoses or tubes
- Loose fuel vapor hose or tube connections to the EVAP system components
- A damaged fuel tank pressure sensor
Although this code refers to a “gross” (large) leak, this is an emission standard specification for a disconnected or cracked fuel EVAP canister tube or EVAP canister purge outlet tube. However, the leak may appear really small.
What are the Symptoms of a Large Leak?
Because your EVAP system only handles emissions, you won’t likely see any decrease in the overall performance of your vehicle. Over time, you may notice a slight decrease in fuel economy. When stored in a garage or closed space, you may smell fuel vapors. The worst symptom, however, is increased emissions polluting your environment.
How to troubleshoot P0455
Use these tips to diagnose and fix a P0455 code accurately:
Scan for other codes
Use a code reader to check for other related trouble codes. These may provide additional clues to the underlying problem. Other common diagnostic trouble codes to look for include:
- P0440, P0442, and P0456: Indicate issues with the EVAP system that are similar to P0455 but might point to smaller leaks or general malfunctions
- P0441: Points to problems with the purge flow, which could help identify if the issue is related to the purge valve or flow path
- P0443: Suggests an electrical issue with the purge control valve circuit
- P0446: Indicates a problem with the vent control circuit, which can help focus on the vent valve and associated components
- P0450-P0454: These codes specifically relate to the EVAP pressure sensor. Issues with this sensor can affect leak detection and overall system performance
- P0457: This code means that the gas cap is loose or damaged
Clear the code and test drive
Use the OBD2 reader to clear the trouble codes. Then drive your car for a day.
After the drive, scan the car to see if the same problem reappears. If not, it might’ve just been a one-time occurrence. But if the issue is here again, it means there’s a real problem that needs further action.
Check the gas cap and seals
Make sure the gas cap is tight and undamaged. Check the condition of the rubber O-ring and replace it if necessary. A loose or damaged gas cap is the most common cause of code P0455.
Use a smoke machine
A smoke test can help locate EVAP leaks by filling the system with smoke and observing where it exits. This method is very effective for leaks.
Inspect EVAP hoses
Check for cracks, holes, or disconnected hoses. Replace any damaged ones.
Examine the fuel tank
Inspect the fuel tank for signs of damage or leaks. If necessary, repair or replace the tank. A cracked fuel tank can leak fuel vapor and cause fire.
Check the leak detection pump
Ensure that the EVAP leak detection pump is working properly. If it’s defective, it might incorrectly detect a leak. Replace the pump if necessary so you can detect leaks accurately.