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P0442: Evaporative Emission Control System Leak Detected (Small Leak)

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What is P0442?

Engine code P0442 stands for “Evaporative Emission Control System Leak Detected (Small Leak)”. It’s a diagnostic trouble code that indicates problems with the Evaporative Emission Control (EVAP) System. 

The EVAP system consists of the fuel tank, a charcoal canister, valves, hoses, and a sealed fuel tank gas cap. It prevents gasoline vapor or fuel vapor from escaping into the atmosphere via the fuel tank and fuel system. These vapors are then systematically sent to the engine to be burned off. 

The vehicle computer regularly checks for leaks within this system using the fuel tank pressure sensor, either by pumping in air or pulling a vacuum pressure and measuring the time it takes to reach a certain level. 

So when the leak detection pump detects a small leak within the EVAP system, it alerts the ECU and triggers code P0442.

Common symptoms

Engine code P0442 usually doesn’t manifest itself in noticeable signs. That being said, it does exhibit a few common EVAP code symptoms that you could look out for, like: 

1. An Illuminated Check Engine Light

It’s almost impossible to physically detect an EVAP leak. So when the leak detection pump in the exhaust system suspects an EVAP system leak event, it immediately turns the Check Engine Light on. 

While the engine light doesn’t necessarily indicate trouble code P0442, it’s a good idea to get your car checked. 

2. Poor Gas Mileage Due To The EVAP Leak

When the EVAP vent solenoid and EVAP purge solenoid don’t open as they should, your gas mileage might be negatively affected. The vapors in your car used in combustion will get vented via the EVAP canister, using up some of the fuel that usually goes towards burning.

You may sometimes also notice a fuel smell coming from the engine due to the leaking gasoline vapor.

3. A Failed Emissions Test Or Smoke Test

One of the main indicators of code P0442 is a failed emission test or a smoke test. 

A smoke test is performed to find hard-to-detect fuel vapor leaks. This is done by using a specialized smoke machine that adds pressure to the fuel system and adds smoke so that small leaks will be visible.

Can I still drive?

Trouble code P0442 is generally considered to be a mild code. It doesn’t show any adverse symptoms and is pretty safe to drive with. 

That being said, an EVAP control system leak may be leaking fuel vapors into the atmosphere, which can be rather dangerous. So it’s best to contact a mechanic if your vehicle fails an emissions test.

P0442 causes

Trouble code P0442 can be caused by various factors pertaining to the Evaporative Emissions Control system. 

These may include: 

  • A faulty or loose fuel cap
  • Using an incorrect fuel filler cap or filler tube
  • Damaged fuel pump
  • EVAP system line leak
  • Charcoal canister leak
  • Fuel tank leak
  • Faulty fuel tank pressure (FTP) sensor
  • Damaged or leaking fuel vapor hose or hose clamp
  • Malfunctioning vent valve or purge valve (leaking internally)
  • Faulty or damaged EVAP vent solenoid or EVAP purge solenoid
  • Failed leak detection pump, etc

Diagnosis

Since code P0442 indicates an Evaporative Emission System leak, it needs careful diagnosis and resolution. A small leak in the EVAP system can be harmful to the environment and the car owner, so it’s recommended that you seek prompt help. 

Keeping that in mind, here’s how your mechanic would diagnose trouble code P0442: 

  1. When detecting an EVAP trouble code, the first thing is to connect the OBD-II scanning tool to the engine and check which codes show up. 
  2. They’ll start by inspecting the gas cap. A loose or damaged fuel cap or incorrectly placed fuel filler cap can trigger code P0442. 
  3. Once the fuel cap is tightened or repaired, your mechanic will clear all codes to check if they show up again. If they do, additional diagnosis is needed.
  4. Your mechanic will check for a cracked or disconnected EVAP hose near the engine air box.
  5. They’ll inspect the fuel tank and charcoal canister for damage and leaks and check the purge volume control valve and purge solenoid for proper operation.
  6. They’ll examine the charcoal canister vent control valve to make sure it’s working properly. 
  7. If everything else is working fine, the EVAP leak may be too small to diagnose physically. In that case, they’ll run a smoke test to detect the leak.

Possible repairs for P0442 & Costs

Since there are many potential issues that can cause an Evaporative Emission System leak, trouble code P0442 can be resolved by a combination of various repairs. These include:

  • Tightening the fuel cap
  • Replacing the gas cap
  • Cleaning the gas tank and gas cap with WD-40 cleaner
  • Replacing the EVAP canister purge valve
  • Replacing the EVAP purge solenoid
  • Replacing the charcoal canister or the EVAP line (rare)

Code P0442’s repair costs can range anywhere from $50-$600 (excluding labor), depending on the severity of the issue. To that, you can add about $75-$150 in labor charges

Here’s a closer estimate:

  • Gas cap replacement:  $20-$60
  • EVAP line replacement:  $50-$100
  • EVAP purge valve: $150-$200
  • Charcoal canister vent control valve: $150-$200
  • Charcoal canister replacement: $200-$600

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