|
|
When engine is off, fuel vapors are vented into charcoal canister. When engine is warmed to normal operating temperature and running at speeds greater than idle, PCM energizes purge control solenoid valve, allowing vacuum to purge valve. Canister vapors are then drawn through solenoid valve into intake manifold for burning. Purge control solenoid valve remains closed during idle and engine warm-up to reduce HC (hydrocarbons) and CO (carbon monoxide) emissions. POSITIVE CRANKCASE VENTILATION (PCV) VALVE PCV valve operates in closed crankcase ventilation system. Closed crankcase ventilation system consists of PCV valve, oil separator, breather and ventilation hoses. PCV valve is a one-way check valve located in valve cover. When engine is running, manifold vacuum pulls PCV valve open, allowing crankcase fumes to enter intake manifold. If engine backfires through intake manifold, PCV valve closes to prevent crankcase combustion. SELF-DIAGNOSTIC SYSTEM NOTE: PCM diagnostic memory is retained by direct power supply from battery. Memory is not erased by turning off ignition, but it will be erased if battery or PCM is disconnected. Self-diagnostic system monitors input and output signals through the Data Link Connector (DLC). Diagnostic Trouble Codes (DTCs) can only be read using a scan tester. For additional information, see G - TESTS W/CODES article. Malfunction Indicator Light (MIL) MIL (CHECK ENGINE light) comes on when ignition is turned on. MIL remains on for several seconds after engine has started. If an abnormal input signal occurs, MIL comes on and code is stored in memory. If an abnormal input signal returns to normal, PCM turns MIL off, but code remains stored in memory until it is cleared. If ignition is turned on again, MIL will not come on until PCM detects malfunction during system operation. |