Century V6-173 2.8L VIN W FI (1987)
Wiring Diagram
Circuit Description:
Canister purge is controlled by a solenoid that allows manifold vacuum to purge the canister when deenergized. The ECM supplies a ground to energize
the solenoid (purge "OFF"). The purge solenoid control by the ECM is pulse width modulated (turned "ON" and "OFF" several times a second). The
duty cycle (pulse width) is determined by the amount of air flow, and the engine vacuum as determined by the MAP sensor input. The duty cycle is
calculated by the ECM and the output commanded when the following conditions have been met:
Engine run time after start more than 3 minutes.
Coolant temperature above 80 degrees C.
Vehicle speed above 5 mph.
Throttle off idle (about 3%).
Also, if the diagnostic test terminal is grounded with the engine stopped, the purge solenoid is de-energized (purge "ON").
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 energized in this step; so it should be closed.
2.
Checks for a complete circuit. Normally there is ignition voltage on CKT 39 and the ECM provides a ground on CKT 428.
3.
Completes functional check by grounding test terminal. This should normally de-energize the solenoid opening the valve which should allow the
vacuum to drop (purge "ON").
