P0456

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

CIRCUIT DESCRIPTION

DTC Detection Condition:

The vapor pressure sensor and 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 is shown in the table.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions Part 1:

Typical Enabling Conditions Part 2:

Typical Malfunction Thresholds:

The evaporative emission system consists of the vapor pressure sensor, the CCV (Canister Close Valve), the pressure switching valve and the EVAP VSV (Purge VSV), and those are used to detect malfunctions 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 pressure and the diagnostic test will not executed.

The ECM performs the following steps:
a. Closes the CCV (shutting the system)
b. Checks the stability of the fuel tank pressure. The diagnostic is disabled if the pressure change is more than the specified value.
c. Opens the EVAP VSV. This introduces a negative pressure from the intake manifold to the fuel tank.
d. Closes the EVAP VSV to seal the fuel tank for storing the negative pressure.
e. Monitors the increase in fuel tank pressure for:
1. Rapid increase in the internal pressure, i. e. a large leak: 0.040" or more
2. A pressure rise just above normal, i. e. a small leak: 0.020".

If the ECM detects either of the above conditions, it will interpret this as a leak in the EVAP system. The ECM will illuminate the MIL (2 trip detection logic) and set a DTC.

MONITOR RESULT
The test value and test limit information are described as shown in the table. Check the monitor result and test values after performing the monitor drive pattern.

- TID (Test Identification Data) is assigned to each emissions-related component.
- TLT (Test Limit Type):
If TLT is 0, the component is malfunctioning when the test value is higher than the test limit.
If TLT is 1, the component is malfunctioning when the test value is lower than the test limit.

- CID (Component Identification Data) is assigned to each test value.
- Unit Conversion is used to calculate the test value indicated on generic OBD II scan tools.

INSPECTION PROCEDURE