engine light on after all parts replaced

Question

did not pass the smog test. replaced distributor cap, solenoid, filters and vapor sensor.  the system pressure sensor/switch is low

Answer 1

P0452 Fuel tank pressure sensor low voltage

P0440 Evap system fault

If you set these 2 code together P0452 is invalid. The condition for setting a P0440 is that P0452 is not set, because a P0440 is set a P0452 is invalid, P0452 is usually the purge flow gets slightly stuck open , you can determine this by using fuel trim , if the purge is slighty stuck open the fuel tank pressure sensor voltage goes low.