Circuit Description

PCM will test EVAP system for the following conditions:

• Large and small leaks (P0440 and P0442).
• Excess vacuum (P0446).
• Purge flow during non-commanded condition (P1441).
• Fuel pressure and level sensor faults (P0452, P0453, P0461, P0462 and P0463).
• EVAP purge and vent valve faults (P1645 and P1646).

PCM monitors amount of vacuum in EVAP system by monitoring the fuel tank pressure sensor. PCM will turn off EVAP purge valve and will turn on EVAP vent valve when conditions for setting this DTC have been met. This test indicates a leaking EVAP purge valve or low during non-purge, if fuel tank pressure sensor indicates increasing fuel tank vacuum. DTC will set after 2 consecutive test failures or an increase in vacuum pressure in EVAP system is monitored.