Monitor Description

When 5 hours have elapsed after the ignition switch is turned OFF, the electric vacuum pump creates negative pressure (vacuum) in EVAP system. Then ECM monitors for leaks and actuator malfunctions based on EVAP pressure.

Fig 1: Monitor Description Chart

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Fig 2: EVAP Leak And Pressure Measurement Checking System Diagram (A-D)

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1. Check valve stuck open (P2421)

   For order E, the vacuum pump creates negative pressure (vacuum) in the EVAP system and the pressure is measured. If the pressure increases over 1.9 mmHg (0.25 kPa) within 10 seconds after the vacuum pump is turned OFF, the ECM determines that the check valve is stuck open. The ECM illuminates the MIL and sets DTC (2-trip detection logic).

Fig 3: Evap Pressure Leak Graph (Check Valve Stuck Open)
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2. Check valve stuck closed (P2422)

   For order C, the vacuum pump creates negative pressure (vacuum) through 0.02 inch orifice and the pressure is measured. If the pressure is higher than -7.5 mmHg (-1 kPa) or lower than -33.75 mmHg (-4.5 kPa), the ECM determines that the check valve is stuck closed. The ECM illuminates the MIL and sets a DTC (2-trip detection logic).

Fig 4: Evap Pressure Leak Graph (Check Valve Stuck Closed)
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