P0442 Diagnostic Test Code (DTC) Details - 2001 Chevy Venture

General Description: P0442 Evaporative Emission (EVAP) System Small Leak Detected
Detailed Description:
The Evaporative Emission system is tested for a small leak by applying a vacuum to the system and then monitors for any 'decay' (drop) in that vacuum.  The fuel tank pressure sensor, which is mounted on the top of the fuel pump assembly, is used to do the monitoring.  The Powertrain Control Module (PCM - or engine computer) controls the EVAP canister purge valve and the EVAP vent valve to draw a vacuum (using engine vacuum) on the system.  The PCM then seals the system and monitors for any leaks.  If it detects any leak above a calibrated amount, the P0442 code sets (turns on) in the computer.

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.  The solenoids around the EVAP canister have also been know to get dirty when driving a lot on dirt roads.  A 'smoke test' may be required to detect these small leaks.

Location of main sensor:
The fuel tank pressure sensor is located above the gas tank, on top of the fuel pump assembly.

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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