[EVAP Leak Test Diagnosis]

To perform NVLD Leak Test Diagnosis, ECM software skips the normal process and starts diagnosis directly after Leak Test Diagnosis requests. When Leak Test Diagnosis is requested by external tool, ECM requests HCU to stop engine. When the engine stops, ECM fully opens PCSV to check NVLD pressure switch stuck failure and to stabilize tank pressure before starting Leak Test Diagnosis. If any switch stuck failure is detected, Leak Test Diagnosis ends and reports the results via tool.

After checking switch stuck and pressure stabilization, ECM requests HCU to run engine and the target idle is 1500rpm for running stability. ECM opens PSCV and checks NVLD pressure switch position until the switch is closed. The longer switch closed time is, the bigger leak size can be estimated. ECM converts the switch closed time into leakage size and reports the results. If no leakage or small leak is detected, Leak Test Diagnosis ends. But if large leakage failure is detected, the process goes to the next step.

When any large leak failure is detected at previous status, ECM performs PCSV stuck diagnosis to check the root cause to make large leak. ECM opens PCSV and checks the diagnosis results. If the diagnosis results are acceptable, ECM finishes Leak Test Diagnosis and confirms large leakage failure. But if the results are out of range, ECM tries PCSV plausibility diagnosis max 3 times. When the results are still unsatisfactory even after 3 trials. ECM confirms PCSV stuck failure and reports the results.

If any conditions are not satisfied, ECM stops the process and reports the cancel reason via scan tool. An engineer can check the root cause and solve the problems to cause stop the process.