Without mincing words, the P0442 code is one of the most challenging codes to handle, as a DIY mechanic. The code simply reads: “EVAP system leak detected (small leak)”. But, don’t be fooled: you could easily go a whole month trying to find the leak without making any headway!
So, what’s the smartest way to resolve this code? Is this a code you can resolve in a DIY fashion? If so, what’s the best approach to it?
I’ll answer everything below but first things first: why does the P0442 code set in the first place?
Article Outline
Why the P0442 Code Sets
The Diagnostic Trouble Code (DTC) P0442 is set when the Engine Control Module (ECM) detects that vapor gases that ought to be trapped in the Evaporative Emission Control System (EVAP) are leaking into the environment.
Usually, such leaks are small (between 0.2 and 0.4 inches) and generally present no other issues or challenges.
However, unsorted, they may cause you to fail emission tests, cause physical discomfort while driving and in some cases, cause a dip in MPGs.
So, while the P0442 code indicates a minor issue, it should be treated as soon as practical to avoid other issues cropping up.
How Do You Determine You Have a P0442 Code?
When you have an EVAP leak in your vehicle that meets the specs the ECM sets for the P0442 code, you’ll have a Check Engine Light (CEL) illuminate on your instrument cluster.
The small (usually red) engine sign on your dash is the clue to plug in your OBD II code reader to figure out what exactly could be wrong (since the codes don’t usually pop up directly).
An affordable glove box code reader, like the Foxwell NT301, will help isolate the issue and also point out what you should be looking at.
However, if you don’t have a code reader or aren’t interested in buying one, a shop with one will usually scan the vehicle and charge you for the fix.
Usually, some shops charge for diagnostics separately from the actual work. That said, most shops will be happy to handle the task for you, free of diagnostic cost, if they’re certain that they will be handling the actual fix.
So, what causes the P0442 code? It turns out, not much.
Common Causes of the P0442 Code
The common causes of the P0442 code are simple and straight to the point. I’ll start from the most common and proceed to the most rare.
1. Bad/Loose/Wrong Gas Caps
The gas cap is one of the most ignored parts of a vehicle. From the factory, most vehicles go 10-20 years without changing the gas cap or even inspecting it.
Eventually, the gas cap seals go bad, causing gasoline vapors to escape into the atmosphere – something that shouldn’t happen in the first place.
In such an instance, simply buying another gas cap restores the issue brilliantly.
However, that’s not all. Sometimes, the gas cap is simply loose from a refueling attempt that doesn’t properly close up the unit.
Usually, the instructions of how the cap should be closed are printed on the body of the cap which is usually to the effect of tightening past at least a few clicks.
Failure to follow such express instructions will make the gas cap seal improperly and cause the P0442 code to set.
Yet still, in some instances, it’s simply a case of not using the right gas caps. Many vehicle owners simply slap any gas cap they come across on their gas tanks, once it appears to fit.
While a gas cap may physically fit, most times, external fitting doesn’t necessarily translate to internal fitting, and this results in leaks, eventually.
2. A Cracked EVAP Hose
Hoses are brittle little things; made of rubber, they eventually crack and give way. This happens sooner than later and much more often than you’d love to believe as a vehicle owner.
Now, when EVAP hoses go brittle and crack, they leak out the gases they’re supposed to contain in the first place.
Usually, the leak takes the form of a hairline crack and from there, things expand and take a larger form, especially for hoses that are taken off periodically.
The good part is that hoses don’t just crack; they usually first go brittle before doing their thing.
If you touch a hose and it’s not pliable and soft (as it should be), great chances are that it’s going bad already.
Changing it at that point is smarter than waiting for a leak before considering remediation.
3. Loose Connections
Not all the times are leaks, inspired by hoses, responsible for the P0442 code. Sometimes, the challenge comes from loose hose connections or old hose clamps and not the actual hoses themselves.
A traditional hose, usually, ought to be fastened with clamps. Unfortunately, these clamps get weak with use and reuse and eventually, need to be replaced.
When not replaced after being weakened out, they simply fail to create a perfect seal – and an imperfect seal will leak out gasoline vapors meant to be trapped and kept in the system.
4. A Leak in the Charcoal Canister
A charcoal canister has a singular major function: trapping and retaining gasoline vapors from the fuel tank to be burned at a later time via regular engine combustion.
However, sometimes, this canister itself is faulty and leaks, becoming incapable of securely keeping the gasoline vapors it traps.
When this happens (either due to an accident, carelessness, or the poor positioning of the canister from the factory), the P0442 code is set.
5. A Leaking Fuel Tank or Compromised Fuel Line
From the discussion so far, you can see a pattern: all the challenges of this CEL come from the gas tank and its vapors. So, what happens to the tank itself when things go bad?
While rare, sometimes, the cause of a P0442 code is the gas tank itself or the fuel lines arising from the tank.
Fortunately, great chances are that this WON’T be your challenge, given that both the tank and fuel lines are designed in a superior manner (because of their importance and centrality). A compromise from this point is thus, usually, rare.
Remember, however, that ‘rare’ doesn’t mean impossible…it’s still a potent channel of investigation when the code pops up and shouldn’t be ignored, especially if and when other pointers all tick out fine.
The Easiest Way to Fix a P0442 Code, DIY Style
It’s difficult to address the P0442 code without the requisite tools: it’s at best guesswork, parts throwing, and blind faith.
However, if you have either the ST201 or ST203 smoke machines, then, it’s easy peasy: simply smoke the EVAP system, and smoke will escape at the spot where the leak exists.
‘Following the leak’ like I love to say will be the next logical thing to do and if you’re DIY-inclined, you should be able to handle the challenge, especially if you have a good smoke machine.
However, if you don’t have a smoke machine (or are not mechanically inclined), I’ll advise that you let a mechanic handle the challenge for you.
If you’re going this route, make sure that the mechanic has a smoke machine and smokes the vehicle before proceeding with repairs.
This is important because while a mechanic may visually spot a compromise, there may be more than one such compromise – with the second one hidden in a hard-to-find or reach location. In such an instance (and this happens all the time) only a smoke machine will stop the job from being done twice.
Can You Drive With a P0442 Code? How Serious Is It?
A P0442 code isn’t a very serious DTC and you can certainly drive with it without any adverse effects.
However, like most vehicle issues, not sorted on time, it’s likely to develop into something more serious which will cost you much more to fix, down the line.
To avoid this scenario (and avoid the potential discomfort and health challenges of inhaling gas vapors in the cabin), schedule a check at the earliest convenience or if you’re DIY inclined, check out the issue and smoke the vehicle as soon as it’s practical.
Good luck.