System Diagnosis - EVAP Canister Purge System

Important: Perform a careful visual inspection of the Evaporative Emission (EVAP) system components and connecting hoses before diagnosis of an EVAP system malfunction.

PROCEDURE
1. Allow the engine to cool to room temperature.
2. Start the engine (cold).
3. Disconnect the purge hose from the EVAP canister.
4. Place a finger against the end of the disconnected hose and check for vacuum. Vacuum should not be felt when the engine is below normal operating temperatures.
5. Connect the purge hose to the EVAP canister and warm the engine up to normal operating temperature.
6. Disconnect the purge hose from the EVAP canister.
7. Place a finger over the disconnected hose and check for vacuum. Vacuum should be felt with the engine running at normal operating temperature.

Notice: The EVAP canister purge system does not perform purging (vacuum is not detected at the purge hose) unless the engine is sufficiently warmed up and the Heated Oxygen Sensor (HO2S) is fully activated. When the purge hose is disconnected as in Step 5, some air may be drawn into the purge line. As a result, the PCM might detect a change in the purge gas concentration and stop purging. This is a normal action and may be the cause of a failure to detect vacuum in Step 6. If no vacuum is felt in Step 6, continued testing of the EVAP system may be necessary to avoid replacement of good parts.

Failure of the Evaporative Emission (EVAP) Canister Purge System to pass any of the above checks indicates a possible malfunction that will require further inspection.