Evaporative emission leak detection pump

The leak detection pump is built into the canister pump module.

The description can be found in the evap (evaporative emission) system (see page es-335).

Refer to the evap system (see page es-340).

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.

*: 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 to off, the monitor check starts 2.5 Hours later.

*: If only a small amount of fuel is in the fuel tank, it takes longer for the evap pressure to stabilize.

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 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).

2. 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).

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.

"Saturated" indicates that the evap pressure change is less than 0.286 Kpa-g (2.14 Mmhg-g) in 60 seconds.

Refer to checking monitor status (see page es-17).