P0455

DTC P0455 Evaporative Emission Control System Leak Detected (Gross Leak)

CIRCUIT DESCRIPTION

The vapor pressure sensor, canister closed valve (CCV) and pressure switching valve are used to detect abnormalities in the evaporative emission control system.

The ECM decides whether there is an abnormality in the evaporative emission control system based on the vapor pressure sensor signal.

DTC P0442, P0455 or P0456 is recorded by the ECM when evaporative emissions leak from the components within the dotted line in Fig. 1, or when the vapor pressure sensor malfunctions.

MONITOR DESCRIPTION

DTC Detecting Condition:

Monitor Strategy:

Typical Enabling Conditions:

Typical Enabling Conditions (continued):

Typical Malfunction Thresholds:

Monitor Result (MODE 06 DATA):

A leak in the evaporative emission system prompts the ECM to set DTC P0442, P0455 or P0456.

The ECM checks for leaks in the system by introducing a high negative pressure (vacuum) from the intake manifold by commanding the EVAP VSV open while the CCV (vent) is closed and the pressure switching valve is open. After sufficient time has elapsed the fuel tank should have developed a high negative pressure (vacuum) and the EVAP VSV closed. The ECM then monitors the pressure rise (loss of vacuum) in the fuel tank. If the pressure rises too rapidly, the ECM concludes that there is a leak in the system. The ECM will turn on the MIL and set a DTC.

The ECM has separate DTCs for small and large leaks:
1. DTC P0442 is set when the internal fuel tank pressure has a large increase and the EVAP system has a small leak.
2. DTC P0455 is set when the EVAP system has various large leaks. Even though the ECM sends a signal to the EVAP VSV (when CCV is closed) to create a vacuum, the internal fuel tank pressure does not decrease beyond a specified level.
3. DTC P0456 is set when the internal fuel tank pressure increase slightly and the EVAP system has a small leak.

HINT: Refer to DTCs P0441, P0446 and P2418.