Circuit Description

PCM tests the EVAP system for the following:

• Large and small leaks.
• Excess vacuum.
• Purge flow during non-commanded conditions.
• Fuel level and fuel pressure sensor faults.
• EVAP purge and vent valve faults.

PCM monitors the fuel tank pressure sensor in order to determine the level of vacuum/pressure in EVAP system. PCM commands both EVAP purge solenoid and EVAP vent valve on when conditions for running this DTC are met in order to apply engine vacuum to EVAP system.

PCM commands EVAP purge solenoid off once system has reached a predetermined level of vacuum. This test checks is vacuum can be achieved in EVAP system. Failure to develop a vacuum may be caused by a large leak or restriction. This DTC sets after twice failing this test.

Conditions for setting DTC:

• DTCs P0107, P0108, P0112, P0113, P0121, P0122, P0123, P0420, P0430, P0500, P0502, P0503, P1111, P1112, P1114, P1115 and HO2S related DTCs not set.
• Ignition voltage 10-17 volts.
• BARO pressure greater than 75 kPa.
• Fuel level 15-85 percent of full capacity.
• ECT and IAT 39-86°F (4-30°C).
• Start-up engine coolant and intake air temperatures within 16°F (9°C) of each other.