If only a small amount of fuel is in the fuel tank it takes longer for the EVAP pressure to stabilize

Operation A: Atmospheric Pressure Measurement

Purge VSV: OFF

Operation B, E:

0.02 Inch Leak Criterion Measurement

Canister

Canister Pressure Sensor

Canister Pressure Sensor

Canister Filter

Leak Detection Pump: OFF

Fuel Tank

Vent Valve: OFF (vent) Canister Pump Module

Canister Filter

Leak Detection Pump: OFF

OFF (vent)

Reference Orifice (0.02 Inch)

OFF (vent)

Operation C: EVAP System Pressure Measurement

Reference Orifice (0.02 Inch)

Operation D: Purge VSV Monitor y

ON (closed)

(

\

Atmospheric Pressure

Negative Pressure

V

1. P2401: Leak detection pump stuck OFF

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 0.02 inch leak criterion. If the pressure is higher than -1.06

kPa (-7.95 mmHg) , or lower than -4.85 kPa (-36.38 mmHg) , 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).

: The thresholds vary according to the atmospheric pressure measured in operation A. The values described above are based on an atmospheric pressure of 100 kPa (750.1 mmHg): absolute pressure.

EVAP Pressure when Leak Detection Pump Stuck OFF

EVAP Pressure when Leak Detection Pump Stuck OFF

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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