EVAP system test description
- The EVAP system test finds gas leaks or blockage of EVAP system using the changes of the fuel tank pressure.
- This test starts after sending an on-demand test signal from the M-MDS to the PCM.
- This test consists of three stages, and each stage is performed automatically as follows:
Stage 1 test. (Test for large leak or blockage)
- M-MDS send the stage 1 test start signal to the PCM.
- PCM controls the CV solenoid valve and purge solenoid valve to control the tank pressure to the targeted value.
- M-MDS detect the large leak or the purge line blockage if the tank pressure does not arrive at the target vacuum in specified period.
Stage 2 test. (Test for small leak)
- When fuel tank pressure arrived at the targeted pressure at stage 1 test, M-MDS sends the stage 2 test signal to the PCM to turn off the purge solenoid to keep the tank pressure.
- M-MDS detects the small leak if the tank pressure can not be kept within the target of specified period.
Stage 3 test. (Test for blockage)
- M-MDS sends the stage 3 test signal to the PCM to turn off the CV solenoid to check the blockage of EVAP system.
- M-MDS detects blockage of the CV solenoid valve or air filter if the tank pressure does not arrive at the target (atmosphere).