Everything You Need to Know About the P0442 CODE

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The P0442 trouble code is related to the Evaporative (EVAP) Emission Control System.

The Evaporative Emission Control System restrains fuel vapors from escaping into the atmosphere by enclosing the fuel system of the vehicle. 

There could be many causes behind this code. If you’re struggling with the P0442, then this article is for you.

Let’s jump right in!


What Does the P0442 Code Mean?

The PO442 indicates that there’s a small leak in the EVAP system.

When the vehicle engine is turned off, the Electronic Control Unit (ECM) carries out a leak test to double-check that the evaporative emission control system is functioning correctly.

In this test, the ECM seals the EVAP system. If the system maintains the pressure, this means it’s functioning properly. However, if the system doesn’t, then the ECM detects that there’s a small leak.

This leak is usually 0.2-0.4 inches in diameter.

The leakage isn’t a serious problem, and you’ll only notice a few symptoms which we’ll mention in the next section.

Nonetheless, we recommend that you get it fixed as soon as you notice it to prevent further damage.


What Are the Symptoms of the P0442?

The most apparent symptom of the P0442 is the Check Engine Light on the dashboard.

You may also notice a slight dip in the fuel economy of the vehicle, along with fuel smell and increased emissions.


What Are the Possible Causes of the P0442?

  • A Leak in the fuel tank
  • A leak in the charcoal canister
  • A loose gas cap
  • The gap cap isn’t original
  • A leak in the fuel tube
  • A defect in the purge valve

How is the P0442 Diagnosed and Fixed?

Before you begin the diagnosis process, you’ll need the following tools:

  • A scanning tool
  • A ground and fixed wire
  • A smoke tester

Check for Other Codes

The first thing you want to do is to check the vehicle for codes other than the P0442 using a scanning tool. Codes related to fuel pressure or the fuel system need to be repaired first before the P0442.

Visually Inspect the EVAP

You’ll then need to inspect the EVAP system carefully by checking for any visible cracks, broken parts, or damaged pieces.

Take a Look at the Gas Cap

Next, you’ll need to examine the gas cap. If it’s loose, make sure that you tighten it well. If it’s damaged, you’ll need to replace it.

The problem with examining the gas cap is that the damage isn’t always visible. You may want to change the gas cap anyway if it wasn’t loose, and you didn’t notice other issues. 

Test the Purge Volume Control Valve

Examine the purge volume control valve to make sure they’re properly functioning. To do so, remove hoses from both sides of the control valve. The key and the engine should be off at this point.

To test the system, blow through the opening; if you can’t, then they’re sealed properly. In that case, the purge volume control valve isn’t the problem. 

Examine the Charcoal Canister Vent Control Valve

The next step is to inspect the charcoal canister vent control valve. This valve allows air to pass through it with no power source applies. Over time, it may cause leaks as it gets sticky or may fail to operate.

To examine the charcoal canister vent control valve, you must remove hoses from either side with both the key and engine off. The air should pass through when you blow through the opening.

Blow through the openings again, but this time, supply a fused power source to one end and ground to the other of the electrical connector. You’ll know they’re correctly sealed when you can’t blow through them.

Carry Out a Smoke Test

If you try all the previous steps and fail to detect the problem, you’ll need to execute a smoke test on the EVAP system. You could do this using a smoke tester, or you could take your vehicle to a mechanic. 


What are the Common Mistakes When Diagnosing P0442?

The P0442 should be easy to diagnose by any qualified technician. Often, the problem is related to the gas cap.

Overlooking the gas cap could waste a lot of time and effort trying to diagnose the parts of the system.

We recommend you remove the gas cap and reinstall it. You can test drive the vehicle for a day after clearing the code. If the code comes back, try replacing the cap and repeat the process. 

If the problem persists, proceed by checking the other components, as mentioned above.


About the Author JamesL Davis

James is a certified auto technician specializing in commercial vehicles. With 30 years of experience under his belt, James has encountered almost every type of automotive issue there is! Besides his day job at the repair shop, he is also an amateur race car driver.

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