Evaporative Emissions System: Testing and Inspection

Evaporative Emission Canister Purge:

Evaporative Purge Solenoid Valve Circuit.:

Tank Pressure Control Valve:

Functional Check:
Fuel Tank Pressure Control Valve
With hand vacuum pump, apply approximately 38 cm Hg (15" Hg) to the control vacuum tube. After ten seconds, there should be at least 13 cm Hg (5" Hg) vacuum remaining. If after 10 seconds there is less than specified vacuum, replace the valve.
With 38 cm Hg (15" Hg) applied to control vacuum tube, attach a short piece of hose to the valves tank tube side. Blow into the tube. You should feel air pass through the valve. If not, replace the valve.
Inspect
Ensure all connections and vacuum lines are tight and free of cracks, damage and restrictions. Visually check vapor canister for cracks and/or damage.

Circuit Description
Canister purge is controlled by a solenoid that allows manifold vacuum to purge the fuel vapor canister when energized. The PCM supplies a ground to energize the solenoid. IF the output/field service enable terminal is grounded with the engine stopped and ignition "ON", or the following conditions are met with the engine running, the EVAP canister purge solenoid valve will be energized (purge "ON").
^ Coolant temperature above 60°C (140°F)
^ Vehicle speed above 2 mph
^ Throttle off idle, above 1.6%

Test Description
Numbers below refer to circled numbers on the diagnostic chart.

1. Checks to see if the solenoid is opened or closed. The solenoid is normally closed and should open when energized by a Tech 1 or the "output/field service enable" terminal is grounded.
2. This should energize the solenoid valve and allow the vacuum to drop (purge "ON").

Diagnostic Aids
Normal operation of the canister purge solenoid described as follows:
^ With the ignition "ON", engine "OFF", "output/field service enable" terminal grounded, the EVAP canister purge solenoid valve should be energized.