P0440 Diagnostic Test Code (DTC) Details - 2001 Chevy Venture
General Description: P0440 Evaporative Emission (EVAP) System - Large Leak Detected
Detailed Description:
The Evaporative Emission system is tested for a large leak by applying a vacuum to the system (using engine vacuum) and then monitors for any drop in that vacuum.  The fuel tank pressure sensor is used to do the monitoring.  The engine computer (PCM - or Powertrain Control Module) controls the EVAP canister purge and vent valves to draw a vacuum on the system.  The computer then seals the system and checks for any leaks.  If it detects any leak above a calibrated amount, or cannot maintain a vacuum, the P0440 code sets (turns on) in the computer and turns on the check engine light (or service engine soon light).

Conditions for this code to set:
Many other codes (about 23) have to NOT be set, fuel level needs to be between 15 and 85 percent, Engine Coolant Temperature (ECT) and Intake Air Temperature (IAT) should be between 39 & 86 degrees F, the ECT & IAT at start up are within 16 degrees F of each other, and the speed of the vehicle is less than 75 miles per hour. 

What to check for:
Look for a loose or damaged seal at the gas cap, or any of the associated hoses for the EVAP system, including the fill hoses and seals, Also check EVAP vacuum lines for good connections or damage.  The EVAP canister could also be damaged. The solenoids around the EVAP canister have also been know to get dirty when driving on a lot on dirt roads.  A 'smoke test' may be required to detect these leaks, but once this is done the leak should be obvious.

Location of main sensor:
The fuel tank pressure sensor is located above the gas tank, on top of the fuel pump assembly.  The EVAP canister is mounted just in front of the fuel tank.

Notes: Always check for loose wiring or connections, especially if this code is intermittent.  

Important Note: Just because a code names a particular sensor or component, it does not mean that sensor or component is bad. Proper diagnostic procedures (such as a smoke test) may need to be performed to find the root cause of the problem. 

 

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