Evaporative Emissions System: Testing and Inspection

Canister Purge Control Diagnosis:

DFI Emission Circuit:

DIAGNOSIS Numbers below refer to circled numbers on the diagnostic chart.

1. Checking for the canister purge solenoid able to hold vacuum. If the solenoid can't hold vacuum, it should be replaced.

2. Vacuum should release when the solenoid is cycled on an output cycling.

3. Checking for proper vacuum signals from the throttle body.

4. Checking for proper electrical signals to the canister purge solenoid.


CIRCUIT DESCRIPTION

The canister purge solenoid receives 12 volts from the 10 amp number 5 fuse on the underhood relay panel through circuit 639. The ECM energizes the canister purge solenoid by grounding pin A10 (circuit 428). When the solenoid is energized it allows the canister to purge.

The canister is commanded to purge when:

^ Coolant is above 70~C.

^ Closed loop has been achieved for at least 9 seconds.

^ Throttle switch is open.

^ Code E13, E44, or E45 are present.

FUNCTIONAL TEST

1. Disconnect the hose leading from the Tank Pressure Control Valve, (TPCV) to the lower port of the charcoal canister at the caniser end.

2. Attach a hose to the fuel tank port of the TPCV and attempt to blow through it. Little or no air should pass through the TPCV.

3. With a hand vacuum pump, apply vacuum (15"Hg. or 51 kPa) through the TPCV upper tube (manifold vacuum supply port). If the diaphragm does not hold vacuum for at least 20 seconds, the diaphragm is leaking, and the TPCV must be replaced. If the diaphragm holds vacuum, try to blow through the hose connected to the lower tube while vacuum is still being applied. An increased flow of air should be observed. If not, replace the TPCV.

4. Attach a hose to the lower port of the canister and attempt to blow through it. Air should pass into the canister. If not, replace the canister.

5. Disconnect the canister purge solenoid electrical connnector, attach a hose to the upper port of the canister, and attempt to blow through it. Air should not pass into the canister. If air passes, replace the purge solenoid.

6. Measure the resistance of the purge solenoid. Refer to "SPECIFICATIONS". If the solenoid resistance is not in this range, replace the solenoid.

7. Reconnect all purge hoses and the solenoid electrical connector.