P0456

DTC P0442 EVAPORATIVE EMISSION CONTROL SYSTEM LEAK DETECTED (SMALL LEAK)
DTC P0456 EVAPORATIVE EMISSION CONTROL SYSTEM LEAK DETECTED (VERY SMALL LEAK)

CIRCUIT DESCRIPTION

DTC Detection Conditions:

The vapor pressure sensor and the VSV for CCV (Vacuum Switching Valve for Canister Closed Valve), VSV for EVAP (Evaporative Emission), and VSV for pressure switching valve are used to detect abnormalities in the EVAP control system. The ECM determines whether there is an abnormality in the EVAP control system based on the vapor pressure sensor signal.

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

HINT: Typical DTC outputs of each trouble area are as follows.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions (Part 1):

Typical Enabling Conditions (Part 2):

Typical Malfunction Thresholds:

The EVAP (Evaporative Emission) system consists of the vapor pressure sensor, the CCV (Canister Closed Valve), the VSV (Vacuum Switching Valve) for pressure switching valve and the VSV for EVAP (Purge VSV). These are used to detect malfunctions in the system by the ECM.

An EVAP leak test is run once per driving cycle, when the ECM detects that the vapor pressure in the fuel tank has stabilized. However, if the vehicle is being driven on rough or winding roads, the diagnostic EVAP test is not executed because the movement of the fuel in the tank prevents the vapor pressure stabilizing.

The ECM conducts the following operations for an EVAP leak test.
a. Closes the CCV (to shut the EVAP system).
b. Checks the stability of the internal fuel tank pressure. (If the variation in the internal pressure is greater than the specified value, the ECM cancels the test.)
c. Opens the VSV for EVAP (to seal the fuel tank for storing the negative pressure).
d. Monitors the negative pressure in the fuel tank for:
1. A rapid decrease, i.e., a large leak: 0.040 inch or more hole leak
2. A decrease greater than the normal level, i.e., a very small leak: 0.020 inch hole leak

If either one of the leaks, (1) or (2), described in operation d. above is detected, the ECM determines that there is a leakage from the EVAP system, and then illuminates the MIL and sets a DTC (2 trip detection logic).

MONITOR RESULT

Refer to Checking Monitor Status for detailed information. Mode 6 Data

INSPECTION PROCEDURE

HINT: Read freeze frame data using a hand-held tester or OBD II scan tool. Freeze frame data record the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data, from the time the malfunction occurred.