EVAP system leak inspection using the M-MDS

EVAP system test out line 

• The EVAP system test, which can 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.

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.
      Fig 1: EVAP System Test (Large Leak Or Blockage)

      
    • 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.
      Fig 2: EVAP System Test (Small Leak)

      
    • 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 for blockage of EVAP system.
      Fig 3: EVAP System Test (Blockage)

      
    • M-MDS detects blockage of the CV solenoid valve or air filter if the tank pressure does not arrive at the target (atmosphere).

  EVAP system malfunction judgment 

• M-MDS detects the small/large leak or blockage based on fuel tank pressure at the end of EVAP Test.
  Fig 4: EVAP System Malfunction Judgment Chart

  

  Evaporative system test procedure 

• Verify that all PIDs are within the following specifications.
  Fig 5: PIDs Specifications Chart

  
  NOTE:

  • To successfully perform this procedure, all PIDs must be within the specifications before proceeding to the next step.
• Select the following items from the initialization screen of the M-MDS.
  • Select "Powertrain".
  • Select "Fuel".
  • Select "EVAP Test".
    • Verify that ECT and IAT are within specifications at the confirmation screen. To successfully perform this procedure, ECT and IAT must be within the spec before proceeding to the next step.
    • Fuel Level must be maintained within 15 %-85 %  . PCM will cancel the EVAP Test If the Fuel Level is lower than 15 %  or higher than 85 %  .
• Verify the test results described on the M-MDS and follow the instructions.