Firebird V8-305 5.0L VIN F FI (1987)
Wiring Diagram for Chart C-3 Canister Purge Valve
Circuit Description:
Canister purge is controlled by a solenoid that allows manifold vacuum to purge the canister when de-energized. The ECM supplies a ground to energize
the solenoid (purge "OFF"). If the diagnostic test terminal is ungrounded with the engine stopped or the following is met with the engine running, the
purge solenoid is de-energized (purge "ON").
Engine run time after start more than 1 minute.
Coolant temperature above 75 degrees C.
Vehicle speed above 15 mph.
Throttle off idle.
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. A shorted solenoid
could cause an open circuit in the ECM.
3.
Completes functional check by ungrounding test terminal. This should normally de-energize the solenoid and allow the vacuum to drop (purge
"ON").
