P0456

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 (Canister Closed Valve) are used to detect abnormalities in the EVAP (Evaporative Emission) 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 figure 1, and when the vapor pressure sensor malfunctions.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Monitor Result (Mode 06):

The ECM checks the EVAP (Evaporative Emission) system using the vapor pressure sensor, CCV (Canister Closed valve), and VSV (Vacuum Switching Valve) for EVAP. The ECM closes the EVAP system and introduces negative pressure (a vacuum) into it. The ECM then monitors the internal pressure using the vapor pressure sensor.
(Refer to figure 1)

The ECM checks for leaks in the EVAP system by introducing a highly negative pressure from the intake manifold, by signaling the VSV for EVAP to open with the VSV for CCV (vent) closed. After sufficient time has elapsed, the fuel tank develops a highly negative pressure and the VSV for EVAP is then closed. The ECM monitors the pressure rise (vacuum loss) in the fuel tank. If the pressure rapidly rises, the ECM determines that there is a leakage from the EVAP system, and illuminates the MIL and sets a DTC. If the leakage is large, DTC P0442 is set. If it is small, DTC P0456 is set.

Wiring Diagram:

Step 1 - 3:

Step 4 - 8:

Step 9 - 10:

Step 11 - 12:

INSPECTION PROCEDURE

HINT:
- If any of DTC P0441, P0446 or P0451 are set simultaneously with DTC P0442 or P0456, first troubleshoot DTC P0441, P0446 or P0451. If no malfunction is detected, troubleshoot DTC P0442 or P0456 next.
- Ask the customer whether, after the MIL came on, the customer found the fuel tank cap loose and tightened it. Also ask the customer whether the fuel tank cap was loose when refuelling. If the fuel tank cap was loose, it was the cause of the DTC. If the fuel tank cap was not loose or if the customer was not sure if it was loose, troubleshoot according to the following procedure.
- 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.
- When the ENGINE RUN TIME in the freeze frame data is less than 200 seconds, carefully check the vapor pressure sensor.