(Solved) EASY FIX for P0442 small EVAP leak on a Dodge Ram

Nov 1

Written By Diagnostic Mechanic

Have a check engine light with the code P0442?

So did this owner of a 2002 Dodge Ram 1500.

In this case study, we will look at how to test the EVAP system and fix the issue for P0442.

What does the P0442 code mean?

The code P0442 means that the engine control module has detected a small leak in the EVAP system. The EVAP system keeps fuel vapors from escaping and causing harm to the atmosphere.

All EVAP codes should be handled with proper care to not increase the emissions of the vehicle.

What is the EVAP system?

The EVAP system works in conjunction with the fuel system on your car. Fuel vapors in your gas tank are trapped by the EVAP system and then used in the engine. The EVAP system prevents fuel vapors to not escape your vehicle.

To learn more about the EVAP system, check out this article.

How do I fix code P0442?

The code P0442 can be a difficult problem to solve because of the size of the leak. Even with proper tooling, like a smoke machine, it can still be difficult to find the leak.

The key is to inspect all of the lines and hoses of the EVAP system for any damage, then test each component for proper function.

In some cases, there actually may not be a leak, but a component failure.

For example, a purge valve or vent valve may be partially stuck open and releasing fuel vapors.

What would cause a P0442 code?

Some possible causes for a P0442 code are old age of rubber lines and faulty parts.

Here is a list of possible areas that can have a small EVAP leak:

Gas Cap
Charcoal Canister (EVAP canister)
EVAP Hose or Vacuum Lines - Rubber hoses can crack and slowly leak.
EVAP purge solenoid (Purge Valve)
Leak Detection Pump or Vent Valve
Fuel Pump Gasket - Located on top of the gas tank, the fuel pump gasket can develop a small leak over time.
Fuel Filler Neck

How much does it cost to fix the P0442 code?

The cost of fixing a P0442 code depends on the location and severity of the leak.

A leak in a hard-to-reach area may require multiple hours to find and repair.

What you'll be paying for is diagnostics and an hour of labor at least. This should include a smoke test to locate the leak.

Can you drive with a P0442 code?

You should always repair any EVAP issue and consult with a professional mechanic if you have questions about driving with an EVAP issue.

When your vehicle has a P0442 code, it is typically okay to drive, but should be looked at as soon as possible.

Case Study

Customer Complaint:

The owner of a 2002 Dodge Ram 1500 came into the shop with a complaint of a check engine light.

When I connected my scan tool to the truck, I found that it had the DTC (diagnostic trouble code) P0442.

The scan tool defined P0442 as "Evaporative Emission System Leak Detected (small leak)".

First Thoughts:

A small EVAP leak may be hard to find.

It could be somewhere in the engine compartment or under the truck. Anywhere there are EVAP lines and components, then that is where I have to look.

Since this truck is pretty old (20 years), I could be looking for a cracked hose or faulty component.

Diagnostics:

The first step I wanted to take on this truck was to connect a smoke machine and put some into the EVAP system.

In most cases, the smoke will come and identify the problem easily.

I connected the smoke machine to the purge valve hose that runs to the rear of the truck, towards the fuel tank and other EVAP components.

When I connect the smoke machine this way, it fills the lines, fuel tank, charcoal canister, and all the other components with smoke.

Once the smoke machine has started filling the system with smoke, I inspect all the lines and components.

Do not forget to check on the top of the fuel tank where the fuel pump is located. The fuel pump o-ring can leak and cause EVAP codes.

When inspecting the truck, I found smoke coming out of two areas. The two areas were actually one EVAP line. See the pictures below.

Smoke coming out of cracked EVAP vent line. This is NOT the leak.

It's important to note that the EVAP system has to vent. When you are trying to find a leak and are using a smoke machine, you have to plug the vent or use a scan tool to close it through the bi-directional controls.

EVAP vent line that was cracked. This is NOT the leak.

The EVAP line that had smoke coming out of it was the vent. It did have a crack in it from old age, but it is not the leak I am looking for.

I know it is not the leak, because the vent for the EVAP system is open to the atmosphere. It will leak smoke out until you plug it. It needs to be plugged to build pressure and smoke to expose the real leak.

Cracked EVAP vent line. This is NOT the leak.

I plugged the vent and started looking some more.

After looking and not seeing any smoke under the hood or under the truck, I looked to see if the gas cap was leaking.

A loose fuel cap or a bad o-ring on the fuel cap can cause a small EVAP leak.

Looking directly at the gas cap, I could not see any smoke coming out, but I put my ear close to it and could hear air coming out.

This was the small EVAP leak I have been trying to locate.

Probably the reason why there was no smoke when I was looking at it was because the smoke had not filled the fuel neck fully. It was pushing out air from the fuel tank and I could hear it.

I took the gas cap off and inspected the o-ring. It was old and needed replacing.

What fixed this truck?

A new gas cap fixed this truck. The old gas cap had a bad seal that was leaking.

It's important to remember that EVAP codes may take a couple days to reappear if the problem was not resolved. Thankfully, we were able to hang on to this truck a few days at the shop to make sure the check engine light did not come back on.

An advanced scan tool can eliminate the need to wait for a couple of days by forcing the truck to do an EVAP leak test. When forcing an EVAP leak test, the vehicle will run all of the tests and monitors of the EVAP system to check for issues. It may only take a few minutes to complete,

This is especially helpful for automotive repair shops that need to get the vehicle back to the customer.

If you suspect your gas cap is bad, try doing a visual inspection. The next time you fill up at the gas station, take a look at the o-ring to see if it is in good shape. It should not be flat or falling apart.

Always remember to tighten the gas cap until it clicks. A loose gas cap can cause the P0442 code and a service engine soon warning light will appear on the dash.

When ordering a new gas cap, make sure to purchase the correct one to prevent fuel vapor leaks. An incorrect fuel filler cap may tighten correctly, but may not seal correctly.

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