Schematic Diagrams

Schematic Diagram

Canister: The canister is filled with activated charcoal and absorbs evaporated fuel vapor from the fuel tank. The collected fuel vapor in the canister is drawn into the intake manifold by the ECM/PCM when the required conditions are met. Purge Control Solenoid Valve (PCSV): The purge control solenoid valve (PCSV) is installed in the passage connecting the canister with the intake manifold. It is a duty-type solenoid valve and is controlled by a signal from the ECM/PCM. To draw the absorbed vapor into the intake manifold, the ECM/PCM opens the PCSV; otherwise, the passage remains closed. Fuel Tank Cap: The ratchet tightening device in the fuel tank cap reduces the possibility of incorrect installation when sealing the fuel tank filler neck. After the seal on the fuel tank cap and the filler neck flange make contact, the ratchet emits a loud click, indicating the seal is installed. Fuel Tank Pressure Sensor (FTPS): The fuel tank pressure sensor (FTPS) is an integral part of the monitoring system. The FTPS monitors the pressure and vacuum level in the fuel tank during PCSV operating cycles and checks the PCSV and the evaporative emission control system for leaks. Canister Close Valve (CCV): The canister close valve (CCV) is located between the canister and the fuel tank air filter. It closes the air inlet to the canister for the evaporative emission control system and prevents fuel vapor from leaving the canister when the vehicle is not operating. NVLD (Natural Vacuum Leak Detection): The NVLD (Natural Vacuum Leak Detection) module is located between the canister and the fuel tank air filter. The NVLD must detect leaks equivalent to a 0.5 mm hole in the fuel tank, canister, and hoses. The NVLD module has a pressure switch and a temperature sensor. The ECM monitors the pressure condition by the temperature change through the pressure switch and temperature sensor and determines whether there is a leak or not. [Normal Diagnosis]

1. 1
   Read Information (READ_INI and INI): Ready to start diagnosis with initialization. Diagnosis starts with the driver's request to start the vehicle (key position at start). When the process begins, the ECM reads the NVLD information and the malfunction information that is stored while the vehicle key is off. The valid air temperature measurement range is from -40°C to 120 °C. "Out of range" is reported if the measured temperature is outside this range. After the request, read the stored values from the NVLD. The following information is received from the NVLD module: air temperature deviation of 6°C for at least 2 hours during soak, check of NVLD switch closed during soak, air temperature sensor plausibility/electrical fault check detected during soak, pressure switch electrical fault check during soak, and reset of malfunctions due to loss of power.
2. 2
   Read Information (SW_VERSION): The NVLD sends an 8-bit software version value when the ECM makes a request.
3. 3
   Read Air Temperature (TAM_SWI_DIAG/READ_TAM): When the ECM requests the air temperature from the NVLD, the measured temperature value is sent to the HCU as an 8-bit value. In case of an "out of range" error, maximum or minimum values are received. During the period whenever the ECM requests the NVLD pressure switch electrical check, the NVLD returns the current and actual values due to the electrical switch error. Because the values from the NVLD may return more than one electrical error at the same time, all errors could have occurred during the engine start phase.
4. 4
   Small Leak Diagnosis (SMALL_LEAK_DIAG): To check for a small leak, the ECM requests the stored information from the NVLD. During soak, the permitted switch closing time is 10 minutes. This means the maximum time can be 2.5 hours (15 × 10 minutes). The switch closing time is transmitted to the ECM.
5. 5
   WAIT: Delay time to wait for the next process.
6. 6
   Large Leak Diagnosis (COMPLETE_DIAG) In this process, the ECM checks for a large leak using the switch check position. During large leak diagnosis, the ECM requests the switch position information, which includes the current switch position and the switch position transition monitored since engine start.
7. 7
   PCSV Plausibility Diagnosis (CPS_CHK) When a large leak error is detected or the switch is closed at engine start-up, the purge control solenoid valve (PCSV) sticking diagnosis is performed by opening the PCSV.
8. 8
   STOP When all diagnosis is completed, the ECM requests the STOP status. During this period, whenever the ECM requests the NVLD electrical switching check, the NVLD returns the current and actual values for electrical switching errors until the end of the drive cycle.
9. 9
   ERROR When any error occurs that prevents continued EVAP monitoring, the ERROR status is set.
10. 10
    OFF When the engine is off with the ignition off, the ECM requests the OFF status. The NVLD is reactivated by a wake-up call at the next drive cycle (ignition switch ON). During this period, the NVLD checks the timer function and reports a malfunction if any problem is detected.
11. 11
    SLEEP If the key-off monitoring conditions for small leak detection are not satisfied, the ECM requests the SLEEP status. No calculations are performed in the NVLD during the key-off period in the SLEEP status.

    

12. 12
    Switch Check and Tank Pressure Stabilization To perform the NVLD leak diagnosis, the ECM software skips the normal process and starts the diagnosis immediately after leak diagnosis requests. When leak diagnosis is requested by the external scan tool, the ECM requests the HCU to stop the engine. When the engine stops, the ECM fully opens the PCSV to check the NVLD pressure switch for sticking and to stabilize the tank pressure before starting leak diagnosis. If any switch sticking fault is detected, the leak diagnosis is terminated and the result is reported through the scan tool.
13. 13
    Small and Large Leak Diagnosis After the switch sticking check and pressure stabilization, the ECM requests the HCU to start the engine, with an idle target speed of 1500 rpm for stability. The ECM opens the PCSV and checks the NVLD pressure switch position while the switch is closed. The longer the switch closed time, the larger the leak size that can be estimated. The ECM converts the switch closed time into leak size and reports the result. If no leak is detected or a small leak is detected, the leak check diagnosis is terminated. However, if a large leak fault is detected, the process proceeds to the next step.
14. 14
    PCSV Plausibility Diagnosis When any large leak is detected in the previous state, the ECM performs the PCSV sticking diagnosis to check the root cause of the increased leak. The ECM opens the PCSV and checks the diagnosis results. If the diagnosis results are acceptable, the ECM ends the leak diagnosis and confirms the large leak fault is not present. However, if the results are out of range, the ECM attempts the PCSV plausibility diagnosis up to 3 times. When the results are still unsatisfactory after 3 tests, the ECM confirms PCSV sticking and reports the result.
15. 15
    Leak Diagnosis Cancellation If any condition is not satisfied, the ECM stops the process and reports the cancellation reason through the scan tool. The engineer can check the root cause and resolve the problem to restart the process.

    

[EVAP Leak Check Diagnosis] Evaporative Emission and ORVR Control System: This system consists of a fill and cutoff valve, a fuel cutoff valve (rollover valve), a two-way valve (pressure/vacuum relief), a fuel liquid/vapor separator installed next to the filler pipe, a charcoal canister installed under the rear floor on the left side member and protector, hoses, and various connectors. When refueling, ambient air is drawn into the filler neck so that fuel vapor is not released into the air. Fuel vapor in the tank is then forced into the canister through the vent valve. The fuel liquid/vapor separator isolates liquid fuel and passes clean vapor to the charcoal canister. While the engine is running, vapor that has entered the canister is drawn into the intake manifold and then into the engine combustion chamber. Using this purge process, the charcoal canister is cleaned and restores its absorption capacity.

1. Fuel Tank Cap 2. Filler Neck 3. Fuel Cut-Off Valve 4. Fuel Tank 5. ORVR Valve 6. 2-Way and Roll-Over Valve 7. Evaporative Hose

8. Evaporation Hose 9. Canister 10. Natural Vacuum Leak Detection Module (NVLD) 11. Fuel Feed Line 12. Purge Control Solenoid Valve (PCSV) 13. Canister Close Valve (CCV) 14. Fuel Tank Pressure Sensor (FTPS)