Trooper LS V6-3.5L (1998)
Canister Purge Control Valve: Testing and Inspection
Circuit Description
Canister purge is controlled by a solenoid valve that allows manifold vacuum to purge the canister. The powertrain control module (PCM) supplies a
ground to energize the solenoid valve (purge "ON"). The EVAP purge solenoid control is turned ON" and "OFF" several times a second. The duty
cycle (pulse width or "ON" time) is determined by engine operating conditions including load. throttle position, coolant temperature and ambient
temperature. The duty cycle is calculated by the PCM and the purge solenoid is enabled when the appropriate conditions have been met:
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The engine run time after start is more than 60 seconds.
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The engine coolant temperature is above 30°C (86°F).
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The fuel control system is operating in the closed-loop mode.
Diagnostic Aids
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Make a visual check of vacuum hoses.
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Check the throttle body for possible cracked or plugged vacuum block.
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Check the malfunction indicator lamp for a possible mechanical problem.
Test Description
The number(s) below refer to the step number(s) on the Diagnostic Chart.
1. Check to see if the solenoid is open or closed. The solenoid is normally de-energized in this step, so it should be closed.
2. This step checks to determine if the solenoid was open due to an electrical circuit problem or a defective solenoid.
3. This should normally energize the solenoid, opening the valve and allowing the vacuum to drop (purge "ON").
