Monitor Description

The two monitors, Key-Off and Purge Flow, are used to detect malfunctions relating to DTC P0441. 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. 1. KEY-OFF MONITOR

5 hours* after the ignition switch is turned OFF, the leak detection pump creates negative pressure (vacuum) in the EVAP system. The ECM monitors for leaks and actuator malfunctions based on the EVAP pressure. HINT:

*: If the engine coolant temperature is not below 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 below 35°C (95°F) 7 hours after the ignition switch is turned OFF, the monitor check starts 2.5 hours later.

Sequ ence

Operations

Descriptions

Duration

-

ECM activation

Activated by soak timer 5, 7 or 9.5 hours after ignition switch turned OFF.

-

Sequ ence

Operations

Descriptions

Duration

A

Atmospheric pressure measurement

Vent valve turned OFF (vent) and EVAP system pressure measured by ECM in order to register atmospheric pressure.

If pressure in EVAP system not between 76 kPa-a and 110 kPa-a (570 mmHg-a and 825 mmHg-a), ECM cancels EVAP system monitor.

10 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.

60 seconds

C

EVAP system pressure measurement

Vent valve turned ON (closed) to shut EVAP system.

Negative pressure (vacuum) created in EVAP system, and EVAP system pressure 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 measured by ECM. Large increase indicates normality.

10 seconds

E

Second reference pressure measurement

After second reference pressure measurement, leak check performed by comparing first and second reference pressure.

If stabilized system pressure higher than second reference pressure, ECM determines that EVAP system leaking.

60 seconds

F

Final check

Atmospheric pressure measured and then monitoring result recorded by ECM.

-

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