EVAP system test outline
- The EVAP system test, which can be substituted for the run drive cycle as an EVAP control system repair confirmation method, can detect the small/large leak or blockage without run-drive cycle.NOTE:
- The M-MDS cannot detect "very small leaks". To identify the leak point, use the leak tester or ultrasonic leak detector.
EVAP system test description
- The EVAP system test finds gas leaks or blockage in the EVAP system using changes in the fuel tank pressure.
- This test starts after an on-demand test signal is sent 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 leaks or blockage)
- The M-MDS sends the stage 1 test start signal to the PCM.
- The PCM controls the CV solenoid valve and the purge solenoid valve to control the fuel tank pressure to the targeted value.
- The M-MDS detects large leaks or purge line blockage if the fuel tank pressure does not arrive at the target vacuum in a specified period of time.
Stage 2 test (Test for small leaks)
- When the fuel tank pressure reaches the targeted pressure during the stage 1 test, the M-MDS sends the stage 2 test signal to the PCM to turn off the purge solenoid valve and maintain the fuel tank pressure.
- The M-MDS detects a small leak if the fuel tank pressure cannot be maintained within the target for the specified period of time.
Stage 3 test (Test for blockage)
- The M-MDS sends the stage 3 test signal to the PCM to turn off the CV solenoid valve and check for blockage in the EVAP system.
- The M-MDS detects blockage in the CV solenoid valve or air filter if the fuel tank pressure does not reach the target (atmosphere).
EVAP system malfunction determination
- The M-MDS detects small/large leaks or blockage based on the fuel tank pressure at the end of the EVAP test.