System Diagnosis - Evaporative Emission Controls (EEC)

Chart C-3:

Wiring Diagram:

CIRCUIT DESCRIPTION:

The canister purge is controlled by a solenoid that allows manifold vacuum to purge the fuel vapor canister when de-energized. The ECM controls the ground to power the solenoid. If the diagnostic test terminal is not grounded, with the engine stopped, or the following exists while the engine is running, the purge solenoid is de-energized (purge "ON").

^ The engine run time is more than one minute.
^ The coolant temperature is above 60~C (140~F).
^ The vehicle speed is above 2 mph.
^ The throttle is off-idle.
^ Block learn and integrator in normal operating range.


TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. This checks to see if the solenoid is opened or closed. It should be normally closed and should open when the diagnostic test terminal is grounded.
2. This completes the functional check by grounding the test terminal. This should normally energized the solenoid and allow the vacuum to drop.

3. This checks for a complete circuit. Normally there is ignition voltage on terminal on circuit 339 of the solenoid connector, and the ECM provides the ground path to circuit 428 of the solenoid connector. A shorted solenoid could cause an open circuit in the ECM.




DIAGNOSTIC AIDS:

This describes the normal operation of the canister purge solenoid.
With the ignition "ON," engine off, and diagnostic test terminal not grounded, the canister purge solenoid will be energized.