OBD II P0442 Error Code Explained

The On Board Diagnostics code P0442 deals with an automobile’s EVAP, or Evaporative Emission Control System.  Its function is to prevent gas vapors from leaking into the atmosphere.

What makes the P0442 code a bad one is that it means a small leak in the EVAP has been detected, and the hole where the leak is coming from may be smaller than a pin-prick.

Because the leak site can be hard to see, a special smoke machine is necessary to locate the damage. The P0442 error code may indicate a necessary visit to a mechanic.

P0442 Technical Description

Evaporative Emission Control System (EVAP) Leak Detected (small leak)

Practical Description

A code P0442 means a small vapor leak in the EVAP has been detected. Leaks from holes as small as 0.04” in diameter can be picked up by the OBD.  As mentioned above, the EVAP is responsible for preventing gas vapors from escaping into the atmosphere from the automobile’s fuel system.

Briefly, in the EVAP, fuel vapors go through hoses towards a charcoal storage canister.  At a later time, when the engine is engaged, the purge control valve of the EVAP will move and allow the intake vacuum to mix the fuel vapors with the engine.

Signs and Symptoms of a P0442

The very small fuel leak may not even be noticeable and the vehicle’s drivability will not be affected.  There may be no symptoms at all.

Why is it a problem?

A fuel system must be sealed in order to prevent fuel from polluting the atmosphere.  A leak means that the fuel will be polluting even if the afflicted vehicle is not in use.  A leak may mean that a car will not pass local emission control requirements and inspections.

Causes and Problems

Causes of a P0442 error code can include the following:

  • An improperly fitting or loose gas cap
  • A small hole in a vapor hose
  • Damaged vent o-ring seals
  • A small leak anywhere in the EVAP system

Some common problems that can cause a P0442 code to appear on the OBD are:

  • Defective fuel caps and damaged fuel tank filler necks
  • A tear or hole in the carbon canister or hoses in the EVAP system
  • A damaged seam in the carbon canister
  • Defective fuel tank sending unit seals and gaskets
  • Damaged EVAP vent and purge valves
  • Damaged fuel tank and fuel tank pressure sensor
  • A broken leak detection pump
  • Hardened 0-rings
  • Loose, worn clamps in the EVAP system

Some common misdiagnoses of a P0442 error code can be a problem with the fuel cap or problems with the evaporative purge or evaporative vent valves.

Possible common repairs that will resolve the P0042 error code

  • Removing and reinstalling the gas cap, clearing all the codes, and driving the automobile for 1 day.  If the codes do not come back, the problem has been solved, if they do, other repairs are in order.
  • Replacing the gas cap with one approved by the automobile manufacturer
  • Inspecting the EVAP system for holes, tears by using a smoke machine and sealing them when they are found.

Cars with these issues are, GMC, Saturn, Chevy, Pontiac, Dodge and many more. as the P0442 code is used by many manufactures.

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