Evaporative emission system reference orifice

The reference orifice is located inside 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 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. P043e: reference orifice clogged

In operation b, the leak detection pump creates negative pressure (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 lower than -4.85 Kpa-g (-36.4 Mmhg-g), the ecm interprets this as a clog malfunction in the reference orifice, and stops the evap system monitor.

The ecm then illuminates the mil and sets the dtc (2 trip detection logic).

2. P043f: reference orifice high-flow

In operation b, the leak detection pump creates negative pressure (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), the ecm interprets this as a high-flow malfunction in the reference orifice, and stops the evap system monitor. The ecm then illuminates the mil and sets the dtc (2 trip detection logic).

"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).