P0442

DTC P0442 Evaporative Emission Control System Leak Detected (Small Leak)

CIRCUIT DESCRIPTION

DTC Detection Condition:

The vapor pressure sensor, canister closed valve (CCV), EVAP VSV 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 or P0456 is recorded by the ECM when evaporative emissions leak from the components within the dotted line in Fig. 1, or when there is a malfunction in the CCV, EVAP VSV, pressure switching valve, or in the vapor pressure sensor itself.

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 CCV (Canister Close Valve), the pressure switching valve and the EVAP VSV (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 pressure and the diagnostic test will not executed.

The ECM perform the following steps:
a. The CCV is closed. (shuts 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 EVAP VSV to introduce a negative pressure (vacuum) from the intake manifold into the fuel tank.
d. Closes the EVAP VSV 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 inch or more
2. Decrease greater than the normal value
If the ECM detects either of above conditions, the ECM interprets this as a leak in the EVAP system. The ECM will illuminate the MIL (2-trip detection logic) and set a DTC.

Wiring Diagram:

INSPECTION PROCEDURE

HINT:
- If DTC P0441 (Purge Flow), P0446 (VSV for CCV), P0451, P0452 or P0453 (Evaporative Pressure Sensor) is output with DTC P0442 or P0456, troubleshoot DTC P0441, P0446, P0451, P0452 or P0453 first. If no malfunction is detected, troubleshoot DTC P0442 or P0456 next.
- Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.
- When the ENGINE RUN TIME in the freeze frame data is less than 200 seconds, carefully check the vapor pressure sensor.