Circuit Description

WARNING: This page is about a different car, the 2000 Isuzu Hombre. However, it is still accessible from the selected car via links, so may be relevant.

EVAP system includes following components: fuel tank, EVAP vent solenoid, fuel tank pressure sensor, fuel pipes and hoses, vapor lines, fuel cap, EVAP emission canister, purge lines, and EVAP purge solenoid.

Evaporative leak detection strategy is based on applying vacuum to EVAP system and monitoring vacuum decay. Vehicle Control Module (VCM) monitors vacuum level by means of fuel tank vacuum sensor input. At a predetermined time, EVAP purge solenoid and EVAP vent solenoid are turned on. This allows engine vacuum to draw a small vacuum on entire EVAP system. After desired vacuum level has been achieved, EVAP purge solenoid is turned off, sealing the system. If a small leak is detected, DTC P0442 will set.

Conditions required to set DTC are:

No ECT, HO2S, IAT, MAP, ODM, or TP sensor DTCs set.
DTC P0125 not active.
Fuel level is greater than 12.5 and 87.5 percent.
BARO is greater than 72.5 kPa.
ECT and IAT is 41-84°F (5-29°C) at engine start-up.
IAT is not greater than 35°F (1.5°C) of ECT at engine start-up.
ECT is not greater than 47°F (8.25°C) of IAT at engine start-up.
Fuel tank level is 12.5-87.5 percent.