Circuit Description

WARNING: This page is about a different car, the 2002 Isuzu Rodeo Sport and 2002 Isuzu Rodeo. However, it is still accessible from the selected car via links, so may be relevant.

Following components are included in Evaporative (EVAP) system:

Fuel tank.
EVAP canister vent solenoid.
Fuel Vapor Pressure (FVP) sensor.
Fuel pipes and hoses.
Vapor lines.
Fuel filler cap.
EVAP emissions canister.
Purge lines.
EVAP canister cut valve (purge solenoid).
EVAP service port.

EVAP leak detection diagnostic strategy is based on applying vacuum to EVAP system and monitoring vacuum decay. PCM monitors vacuum level through FVP sensor input. At an appropriate time, EVAP canister purge valve and EVAP canister vent valve are turned on, allowing engine vacuum to draw a small vacuum on entire EVAP system. After desired vacuum level has been reached, EVAP canister purge valve is turned off sealing system.

A restricted or blocked EVAP canister vent path is detected by drawing a vacuum on the EVAP system, turning Off the EVAP vent solenoid and the EVAP canister purge valve (EVAP vent solenoid Open, EVAP purge PWM 0%) and monitoring fuel tank vacuum sensor input. With EVAP vent solenoid open, any vacuum in system should decrease quickly unless vent path is blocked. A blockage can be caused by following conditions:

Faulty EVAP vent solenoid (stuck closed).
Plugged, kinked or pinched vent hose.
Shorted EVAP vent solenoid driver circuit.
Plugged EVAP canister.

Any of above conditions can set DTC P0446.

When DTC sets, PCM illuminates MIL on second trip after fault was detected. PCM will store conditions present when DTC was set as FREEZE FRAME data in the FAILURE RECORDS data. A history DTC is set.

PCM will turn MIL off on third consecutive trip cycle during which diagnostic runs and fault is no longer recognized. A history DTC will clear after 40 consecutive ignition cycle which diagnostic runs and fault is no longer recognized. DTC can be cleared with scan tool, or by disconnecting battery voltage feed to PCM.