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:

Step 1: Judgement of detection of 0.09 inch leak as normal operation

Step 2: Judgement of detection of 0.02 inch leak as normal operation

Step 3: Detection of 0.02 inch leak

Step 4: Detection of atmospheric air open failure

Step 5: Flickering of the FTP sensor

< Step 1, 2 and 3 proceed simultaneously. Step 4 and 5 proceed simultaneously. >

Step 1:

After the engine has stopped, the engine control module (ECM)/powertrain control module (PCM) monitors the variation of the FTP sensor output to detect "no 0.09 inch leak" depending on the variation corresponding to the pressure inside the fuel tank.

• If the variation corresponding to the pressure is less than a specified value and continues for a specified duration, it is identified as a malfunction of "0.09 inch leak" and the diagnosis completes.
• If the variation corresponding to pressure is more than a specified value before a specified duration has passed, it is defined as "no 0.09 inch leak", judgement of detection of a 0.09 inch leak is completed, and goes to 0.02 inch leak monitor.

Step 2:

After the engine has stopped, the ECM/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 for a specified value or more within a specified duration, goes to step 3.

Step 3:

The ECM/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, reserve identification and the diagnosis is complete.

Step 4:

After the engine has stopped, the ECM/PCM monitors the variation of the FTP sensor output to detect atmospheric air failure, after keeping the canister vent opened for a specified duration to stabilize the pressure inside the fuel tank.

• If the pressure inside the fuel tank after a specified duration has passed deviated exceeding a specified value from the sensor zero point, and if oil is not identified to fuel during EONV is performed, atmospheric air open failure is detected.

Step 5:

After the engine has stopped, the ECM/PCM monitors the variation of the FTP sensor output to detect FTP sensor flickering failure, after keeping the canister vent opened for a specified duration to stabilize the pressure inside the fuel tank.

• If the deviation of pressure inside the fuel tank and an average value after a specified duration has passed exceeded a specified value for more than a specified duration, failure of FTP sensor flickering is detected.