Monitor Description

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:

1. Closed the canister close valve (CCV) (shutting the system).
2. Checks the stability of the fuel tank pressure. If the variation in the pressure is greater than the specified value, disables the diagnosis.
3. Opens the VSV for EVAP to. introduce a negative pressure (vacuum) from the intake manifold into the fuel tank.
4. Closes The VSV for EVAP to seal the fuel tank for storing the negative pressure.
5. 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.