P2401

DTC P2401 EVAPORATIVE EMISSION SYSTEM LEAK DETECTION PUMP CONTROL CIRCUIT LOW




Contents




DTC Summary

Circuit Description







While the engine is running, if a predetermined condition (closed loop, etc.) is met, the purge VSV is opened by the ECM and stored fuel vapors in the canister are purged to the intake manifold. The ECM will change the duty cycle ratio of the purge VSV to control purge flow volume.
Purge flow volume is also determined by the intake manifold pressure. Atmospheric pressure is allowed into the canister through the vent valve to ensure that purge flow is maintained when negative pressure (vacuum) is applied to the canister.

Two monitors are run to confirm proper EVAP system operation.

Key-off monitor
This monitor checks for EVAP system leaks and pump module malfunctions. The monitor starts 5 hours ((+) 15 minutes) after the ignition switch is turned OFF. The 5 hours are required to allow enough time for the fuel to cool down. As a result, Fuel Tank Pressure (FTP) becomes stable and EVAP system monitor will be more accurate. Then, the electric vacuum pump creates negative pressure (vacuum) in the EVAP system and the pressure is measured. Finally, the ECM monitors for EVAP system leaks and pump module malfunctions based on EVAP pressure.

Purge flow monitor
















If EVAP system pressure change is less than 7.5 mmHg (1 kPa) when the engine is running and the purge VSV is turned ON (closed), the ECM determines that the purge flow is insufficient.

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Inspection Procedure

NOTE: When a vehicle is brought into the workshop, leave it as is. Do not change the vehicle condition. For example, do not tighten the fuel cap. Do not disassemble the pump module.

HINT: Using the hand held tester's monitor result allows you to confirm the EVAP system condition.

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.




a. P2401: Vacuum pump stuck OFF
For order C, the vacuum pump creates negative pressure (vacuum) through the 0.02 inch orifice and 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 vacuum pump is stuck OFF (has not operated). The ECM illuminates the MIL and sets DTC (2-trip detection logic).




b. P2402: Vacuum pump stuck ON
If the difference in EVAP system pressure for order A and C is small and is higher than -7.5 mmHg (-1 kPa), ECM determines that the vacuum pump is stuck ON (has been operating throughout order A to C). The ECM illuminates the MIL and sets DTC (2-trip detection logic).

OBD II Monitor Specification:

OBDII Monitor Specification