DTC P0455: Evaporative Emission (EVAP) System Large Leak Detected: General Description
The evaporative emission (EVAP) leak detection system uses an engine off natural vacuum (EONV) method. The EONV method detects leakage from the change in fuel tank pressure via the fuel tank pressure (FTP) sensor with the engine off.
Here is an overview of the malfunction detection for the EONV method:
Judgment 1: Judgment of detection of 0.09 inch leak as normal operation
Judgment 2: Judgment of detection of 0.02 inch leak as normal operation
Judgment 3: Detection of 0.02 inch leak
< Judgments 1, 2, and 3 happen at the same time. >
Judgment 1:
After the engine has stopped, the powertrain control module (PCM) monitors the variation of the FTP sensor output to detect "no 0.09 inch leak" depending on the variation of the pressure inside the fuel tank.
- If the variation of the pressure is a specified value and continues for a specified duration, it is identified as a "0.09 inch leak" and the diagnosis completes.
- If the variation of the pressure is a specified value before a specified duration has passed, it is defined as "no 0.09 inch leak", the judgment of detection of a 0.09 inch leak is completed, and it goes to 0.02 inch leak monitor.
Judgment 2:
After the engine has stopped, the PCM monitors the variation of the FTP sensor output to detect "no 0.02 inch leak" depending on the variation corresponding to the increasing pressure inside the fuel tank.
- If "no 0.02 inch leak" is detected, it is identified as normal; the diagnosis is complete.
- If the pressure inside the fuel tank does not increase a specified value within a specified duration, it goes to Judgment 3.
Judgment 3:
The PCM continues to monitor the FTP sensor output to detect "no 0.02 inch leak" depending on the variation corresponding to the decreasing pressure inside the fuel tank until the detection completes.
- If a "0.02 inch leak" is detected, it is identified as a malfunction; the diagnosis is complete.
- If "no leakage" is detected, it is identified as normal; the diagnosis is complete.
- If the pressure is not atmospheric pressure or less when the detection is completed, that data is stored and the diagnosis is complete.