Circuit Description

WARNING: This page is about a different car, the 2002 Isuzu Trooper. 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 duty solenoid valve.
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 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. If a sufficient vacuum level cannot be achieved, a large leak or faulty EVAP canister purge valve is indicated. This can be caused by following:

Disconnected or faulty FVP sensor.
Missing or faulty fuel filler cap.
Disconnected, damaged, pinched or blocked EVAP purge line.
Disconnected or damaged EVAP vent hose.
Disconnected, damaged, pinched or blocked fuel tank vapor line.
Disconnected or faulty EVAP canister cut valve.
Disconnected or faulty EVAP canister purge valve.
Open ignition feed circuit to EVAP canister purge valve or EVAP canister cut valve.
Damaged EVAP canister.
Leaking fuel sender assembly "O" ring.
Leaking fuel tank or fuel filler neck.

Any of above conditions can set DTC P0440.

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.

PCM will turn MIL off after DTC diagnostic runs and fault is no longer recognized. A history DTC P0440 will clear after 40 consecutive trip cycles during which diagnostic runs and fault is no longer recognized. DTC can be cleared with scan tool, or by disconnecting battery voltage feed to PCM.