Monitor Description
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.
| Sequence | Operations | Descriptions | Duration | ||
|---|---|---|---|---|---|
| - | ECM activation | Activated by soak timer, 5 hours (7 or 9.5 hours) after ignition switch turned to OFF. | - | ||
| 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 will be used in leak check. If EVAP pressure does not stabilize within 15 minutes, ECM cancels EVAP system monitor. |
15 minutes(1) | ||
| 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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- P2401: Leak detection pump stuck OFF
In operation B, the leak detection pump creates negative pressure (a vacuum) through the reference orifice. The EVAP system pressure is then measured by the ECM, using the canister pressure sensor, to determine the reference pressure. If the pressure is higher than -1.057 kPa-g (-7.93 mmHg-g), or lower than -4.85 kPa-g (-36.4 mmHg-g), the ECM interprets this as the leak detection pump being stuck OFF (not operating). The ECM illuminates the MIL and sets the DTC (2 trip detection logic).
- P2402: Leak detection pump stuck ON
In operation B, the leak detection pump creates negative pressure (a vacuum) through the reference orifice. The EVAP (Evaporative Emission) system pressure is then measured by the ECM, using the canister pressure sensor, to determine the reference pressure. If the pressure is higher than -1.057 kPa-g (-7.93 mmHg-g), or lower than -4.85 kPa-g (-36.4 mmHg-g), the ECM interprets this as the leak detection pump being stuck ON (remaining ON all the time). The ECM illuminates the MIL and sets the DTC (2 trip detection logic).
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
HINT:
The detection logic of DTCs P2401 and P2402 is the same because in both cases the reference pressure measured in operation B is compared to the atmospheric pressure registered in operation A. The ECM calculates the difference between these pressures by deducting [the reference pressure] from [the stored atmospheric pressure], and uses this to monitor the EVAP system pressure change.