Circuit Description

Evaporative leak detection strategy is based on applying vacuum to EVAP system and monitoring vacuum decay. Powertrain Control Module (PCM) monitors vacuum level by means of fuel tank vacuum sensor input. At a predetermined time, EVAP purge solenoid and EVAP vent solenoid are turned on. This allows engine vacuum to draw a small vacuum on entire EVAP system. Whenever a sufficient vacuum level cannot be achieved, a large leak or faulty EVAP purge solenoid is indicated.

Conditions for setting this DTC are as follows:

• No TP sensor, ODM, IAT sensor, or MAP sensor DTCs present.
• Start-up ECT 40-86°F (4-30°C).
• Start-up ECT not greater than 14°F (8°C) greater than start-up IAT.
• Start-up IAT not greater than 4°F (2°C) of start-up ECT.
• Fuel tank level is 15-85 percent.
• BARO is greater than 75 kPa.
• Vehicle has been driven at least 11 miles.
• EVAP system is unable to achieve or maintain vacuum during diagnostic test.