P0456

DTC P0456 EVAPORATIVE EMISSION CONTROL SYSTEM LEAK DETECTED (VERY SMALL LEAK)

CIRCUIT DESCRIPTION

DTC Detection Condition:

The vapor pressure sensor and the VSV for the canister closed valve (CCV) 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 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.

HINT: Typical DTC output of each trouble part.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions Part 1:

Typical Enabling Conditions Part 2:

Typical Malfunction Thresholds:

Monitor Result (MODE 06 DATA):

The evaporative emission system consists of the vapor pressure sensor, the canister close valve (CCV), the VSV for pressure switching valve and the VSV for EVAP (Purge VSV), those are used to detect malfunction in the system by ECM.

This test will run once per driving cycle when the ECM detects stable vapor pressure in the fuel tank. While the vehicle is being driven on rough or winding roads, the movement of the fuel in the tank will cause unstable fuel tank vapor pressures and the diagnostic test will not executed.

The ECM performs the following steps:
a. Closed the canister close valve (CCV) (shutting the system).
b. Checks the stability of the fuel tank pressure. If the variation in the pressure is greater than the specified value, disables the diagnosis.
c. Opens the VSV for EVAP to. introduce a negative pressure (vacuum) from the intake manifold into the fuel tank.
d. Closes The VSV for EVAP to seal the fuel tank for storing the negative pressure.
e. Monitors the negative pressure in the fuel tank for:
1. Rapid decrease, i.e. a large leak, 0.040 or more
2. Decrease greater than the normal level.
If the ECM detects either of above conditions, the ECM will interpret this as a leak in the EVAP system. The ECM will illuminate the MIL (2-trip detection logic) and set a DTC.

INSPECTION PROCEDURE