Circuit Description

Evaporative (EVAP) emission system is checked by applying vacuum to the EVAP system and monitoring for a vacuum leak. PCM monitors vacuum level via fuel tank pressure sensor signal. When appropriate, EVAP canister purge valve and EVAP canister vent solenoid are turned on, allowing engine to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, EVAP canister purge valve is turned off, sealing the EVAP system. If a large leak is detected, DTC P0440 will be set under the following conditions.

Conditions required to set DTC are:

• DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134 and P1133 are not set.
• BARO is greater than 72.3 kPa.
• Start-up IAT and ECT is between 38.5-90.5°F (3.5-32.5°C).
• Difference between ECT and IAT at start up is less than 12.2°F (6.75°C).
• Vehicle speed is less than 60 MPH.
• Fuel tank level sensor reads 10-90 percent.
• Fuel counts vary by less than 15 counts in .125 second time frame.
• Maximum engine run time is at least 540 seconds (9 minutes).
• Difference between the actual fuel tank pressure and the expected fuel tank pressure is less than the PCM's expectations.

The listed conditions are met, and the following is met once:

• EVAP system is unable to maintain vacuum, depending upon amount of fuel in fuel tank, during diagnostic test.