Monitor Description
The 2 monitors, Key-off and purge flow, are used to detect malfunctions relating to DTCs P0441-7E, P0441-7F and P0441-9C. The Key-Off monitor is initiated by the ECM internal timer, known as the soak timer, 5 hours after the ignition switch is turned off. The purge flow monitor runs while the engine is running.
- KEY-OFF MONITOR
5 hours* after the ignition switch is turned off, the electric leak detection pump creates negative pressure (vacuum) in the EVAP (Evaporative Emission) system. The ECM monitors for leaks and actuator malfunctions based on the EVAP pressure.
HINT:
*: If the engine coolant temperature is not less than 35°C (95°F) 5 hours after the ignition switch is turned off, the monitor check starts 2 hours later. If it is still not less than 35°C (95°F) 7 hours after the ignition switch is turned off, the monitor check starts 2.5 hours later.
Sequence Operation Description Duration - ECM activation Activated by soak timer 5, 7 or 9.5 hours after ignition switch turned off. - A Atmospheric pressure measurement Vent valve is turned off (vent) and EVAP system pressure is measured by ECM in order to register atmospheric pressure.
If pressure in EVAP system is not between 70 kPa (abs) and 110 kPa (abs) [10.15 psi (abs) and 15.95 psi (abs)], ECM cancels EVAP system monitor.60 seconds B First reference pressure measurement In order to determine reference pressure, leak detection pump creates negative pressure (vacuum) through reference orifice and then ECM checks if leak detection pump and vent valve operate normally. 360 seconds C EVAP system pressure measurement Vent valve is turned on (closed) to shut EVAP system.
Negative pressure (vacuum) is created in EVAP system, and EVAP system pressure is then measured.
Write down measured value as it will be used in leak check.
If EVAP pressure does not stabilize within 15 minutes, ECM cancels EVAP system monitor.15 minutes* D Purge VSV monitor Purge VSV opened and then EVAP system pressure is measured by ECM.
A large increase indicates normality.10 seconds E Second reference pressure measurement After second reference pressure measurement, leak check is performed by comparing first and second reference pressure measurements.
If stabilized system pressure is higher than second reference pressure, ECM determines that EVAP system leaking.60 seconds - Final check Atmospheric pressure is measured and then monitoring result is recorded by ECM. - *: If only a small amount of fuel is in the fuel tank, it takes longer for the EVAP pressure to stabilize.
*1 Purge VSV: Off (Closed) *2 Purge VSV: On (Open) *3 Vent Valve: Off (Vent) *4 Vent Valve: On (Closed) *5 Leak Detection Pump: Off *6 Leak Detection Pump: On *7 Reference Orifice (0.02 inch) *8 Canister Pressure Sensor *9 Canister *10 Fuel Tank *11 Canister Pump Module *12 Canister Filter *a Operation A:
Atmospheric Pressure Measurement*b Operation B, E:
Reference Pressure Measurement*c Operation C:
EVAP System Pressure Measurement*d Operation D:
Purge VSV Monitor*e Atmospheric Pressure *f Negative Pressure - Purge VSV stuck open
In operation C, the leak detection pump creates negative pressure (vacuum) in the EVAP (Evaporative Emission) system. The EVAP system pressure is then measured by the ECM using the canister pressure sensor. If the stabilized system pressure is higher than [second reference pressure x 0.2], the ECM interprets this as the purge VSV being stuck open. If any deterioration has occurred, the ECM will illuminate the MIL and store DTC P0441-7E (2 trip detection logic).
- Purge VSV stuck closed
In operation D, the canister pressure sensor measures the EVAP (Evaporative Emission) system pressure. The pressure measurement for the purge VSV monitor begins when the purge VSV is turned on (open) after the EVAP leak check. When the measured pressure indicates an increase of 0.3 kPa (gauge) [0.044 psi (gauge)] or higher, the purge VSV is functioning normally. If the pressure does not increase, the ECM interprets this as the purge VSV being stuck closed, illuminates the MIL and store DTC P0441-7F (2 trip detection logic).
- Purge VSV stuck open
- PURGE FLOW MONITOR
The purge flow monitor consists of 2 monitors. The 1st monitor is conducted every time and the 2nd monitor is activated if necessary.
- The 1st monitor
While the engine is running and the purge VSV is on (open), the ECM monitors the purge flow by measuring the EVAP pressure change. If negative pressure is not created, the ECM begins the 2nd monitor.
- The 2nd monitor
The vent valve is turned on (closed) and the EVAP pressure is then measured. If the variation in the pressure is less than 0.154 kPa (gauge) [0.022 psi (gauge)], the ECM interprets this as the purge VSV being stuck closed, illuminates the MIL and stores DTC P0441-9C (2 trip detection logic).
Atmospheric pressure check:
In order to ensure reliable malfunction detection, the variation in atmospheric pressures, before and after conduction of the purge flow monitor, is measured by the ECM.