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P0442 OBD-II Trouble Code: Evaporative Emission Control System Leak Detected (Small Leak)

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P0442 code definition

P0442 is a diagnostic trouble code (DTC) that is seen when a evaporative emission control system malfunction is present. This code may be seen with other EVAP system codes.

What the P0442 code means

P0442 is present in vehicles that have a small leak in the EVAP system. The ECU carefully monitors the EVAP system for any leaks or irregularities, when a small leak is detected the ECU set a Check Engine Light to be displayed on the dashboard.

What causes the P0442 code?

  • Faulty or loose fuel cap
  • EVAP system line leak
  • Charcoal canister leak
  • Fuel tank leak
  • Failed vent or purge valve

What are the symptoms of the P0442 code?

  • The Check Engine Light being present on the dashboard.

  • Some vehicles may exhibit a slight drop in gas mileage with the EVAP leak

How does a mechanic diagnose the P0442 code?

  • Hooks up a scan tool to the vehicle's DLC port and checks for any codes present

  • Examines the freeze frame data associated with the code which shows the circumstances that were present with the vehicle at the time of the malfunction

  • Clears the codes and test drives the vehicle

  • Performs a visual inspection of the EVAP system, looking for any obviously cracked or broken components, and loose or damaged EVAP lines

  • Checks for cracks in the fuel tank or charcoal canister

  • Inspects the gas cap for proper fitment and condition, then tests with a gas cap tester

  • Uses a scan tool to monitor tank pressure and confirm if a leak is present

  • Tests the EVAP system solenoids and valves with scan tool

  • Performs a smoke test on the EVAP system, looking for smoke that indicates a vapor leak

Common mistakes when diagnosing the P0442 code

Qualified technicians should have little problem diagnosing P0442 as long as all steps are followed in the proper order and none are skipped.

Commonly, the gas cap is the cause of P0442, if the gas cap is overlooked it can waste time and energy diagnosing other components.

How serious is the P0442 code?

The P0442 generally has no adverse symptoms other than the Check Engine Light being present. When this code is seen, it means that the EVAP system is leaking fuel vapors into the atmosphere. A slight dip in fuel economy may be noticed with this code.

What repairs can fix the P0442 code?

  • Replacing the gas cap
  • Replacing the fuel tank
  • Replacing the charcoal canister
  • Replacing the EVAP system lines
  • Replacing the purge or vent valves

Additional comments for consideration regarding the P0442 code

Professional level tools make diagnosing the P0442 leak much easier and accurate. An advanced scan tool that allows access to live data and control of the EVAP system is very helpful when dealing with the P0442 code or any EVAP code in general.

Some vehicles have the ability to be commanded with the scan tool to test the EVAP system for proper operation of all components, and can be used to help isolate which part of the system the fault or leak lies.

Since they are fuel vapors, most of the EVAP leaks are much smaller than the eye can see. A smoke test is performed to find hard-to-detect fuel vapor leaks. This is done by using a specialized smoke machine that pressurizes the fuel system and adds smoke so that small leaks will be visible.

Need help with a P0442 code?

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The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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