2001 Blazer P0442 EVAP (small leak) ???

I recently had an SES indication and upon reading the code it was a P0442. Referencing this code indicated it was "Evap System Leak (small)".

Does this mean that it's a small vacuum leak or does it mean something else?

Also I noticed that a few days after the PCM coded I began hearing what sounds like a sort of high pitched whine at idle. It almost sounds like a bad water pump but I checked and there are no leaks from the weep or any other system points. When I open the hood and the motor is running I simply cannot hear well enough to pin-point the "whine."

Could a "small" vacuum leak be the cause of this noise?

Thanks, Paul

I recently had an SES indication and upon reading the code it was a P0442. Referencing this code indicated it was "Evap System Leak (small)".

Does this mean that it's a small vacuum leak or does it mean something else?

Also I noticed that a few days after the PCM coded I began hearing what sounds like a sort of high pitched whine at idle. It almost sounds like a bad water pump but I checked and there are no leaks from the weep or any other system points. When I open the hood and the motor is running I simply cannot hear well enough to pin-point the "whine."

Could a "small" vacuum leak be the cause of this noise?

Thanks, Paul

Remove the gas cap and check the rubber seal and see if is is cracked. Buy a new one and replace if necessary. Reinstall the cap and make sure it is on good and tight. The High pithched whine is most likely your fuel pump noise. Some whine is normal, excessively loud is not good.

P0442 indicates a small, (smaller the .030"), leak in the EVAP system. As Rick mentioned, the problem could very well be a faulty fuel cap.

When the ECM runs the EVAP monitor, it activates the Canister Purge Solenoid and the EVAP Vent Solenoid which applies a calculated amount of engine vacuum to the fuel tank. The ECM deactivates both solenoids and monitors how quickly the vacuum decays. If it decays too quickly, depending on the size of the leak, either P0442 or P0440, (large leak), will set.

The EVAP system includes the fuel tank, fuel filler line, fuel cap, fuel tank pressure sensor, fuel pump module "O" ring, EVAP Vent Solenoid, EVAP Purge Solenoid, the purge canister and the lines that connect them all together. EVAP system leaks can be extremely challenging to locate. Along with the fuel filler cap, another common cause is the "O" rings in the EVAP system lines.

We're happy to help you with it, but be aware, it might take some time to diagnose it.

Assuming that no mechanical work has been performed on your fuel system such as replacing the Fuel Pump, or that the truck has not been damaged by a traffic accident or off roading, and the code just appeared out of the blue, the Gas cap is more often than not the culprit. I have seen this code thrown when the gas cap was not tightened up properly or the cap was not re-installed (left on the gas pump) after filling up the tank with gas.

The round rubber seal on the inside of the cap should not show cracking when finger pressure is applied, and the cap should click or make the ratchet sound when tightened. Aftermarket gas caps run about $5 - $10 USD, while OEM Caps at the dealer can go as high as $25 USD.

Almost every Parts store carries them so be sure to get the correct cap for your make and model, take your old one in to the counter and they will also help you determine if you really need to replace your cap.

I do not suggest that you throw money at your truck, Old Master is dead on right. These codes are a bear to fix if it is not the gas cap, but a $5 Gas cap will certainly eliminate that possibility.

Once the cap is replaced, you may need to remove the battery cable for 15 seconds to clear the code and turn the Check Engine light off, but a bit of info here, it may take up to a couple of weeks before the light comes back on if the problem still exists.

You guys were dead on correct with the gas cap. On Monday I looked it over and although there were no cracks, the gasket was worn, brittle and pitted and 2 or 3 spots. Bought a gas cap for $11 and cleared the code with a small reader I own. I have logged over 330 miles since replacing the cap and no light AND no codes. I just read the codes moments ago. All nine (9) monitors are complete and there are no codes of any sort. No "pending" codes either. History with this code showed me that after erasure the code will re-appear after about 24 hours of my driving habit.

Thanks for the tip! That's a load off my mind.

There's just one thing. The whine. That water pump whine that isn't the water pump. When I'm in the truck I could swear it's coming from under the hood but like I said, my hearing ain't what it used to be.

Rick...You mentioned fuel pump and that a little whine is normal. Any way to quantify "Little?"

Thanks again,

Paul

Congrats on the Gas Cap. However, I have seen these things take a couple of weeks to re-appear. Keep your fingers crossed.

O.K. My Bad. Your FUEL pump will make a little bit of a whine. Stand by your gas cap door and have someone turn the key on without starting the engine. You will hear the 2 second prime cycle. The high pitched "whine" should be audible, but not annoying. I recently had an Airtex fuel pump go bad after only 6 months that didn't whine, it "Screeeeeeeched" very loud. It still worked for a couple of days after the screech started, but left me stranded in the middle of the Freeway during rush hour.

Your WATER pump should not "whine" at all. However, I have had a recurring issue in my 2000 Jimmy with Belt noise that drives me crazy and requires a new belt every other year or so to eliminate. It sounds like a pulley bearing going bad, but a new belt solves the problem for a year or so. I suggest that if the noise is under the hood, check the condition of your belt. It may be time for a new one. If the Whine is coming from the gas tank, and seems to be louder than normal, You might want to get a second opinion.

I have had a recurring issue in my 2000 Jimmy with Belt noise that drives me crazy and requires a new belt every other year or so to eliminate. It sounds like a pulley bearing going bad, but a new belt solves the problem for a year or so.

I see that a lot, and not just Blazers. If you look at the inside of the belt you'll see tiny flakes of metal embedded in the rubber. Each one makes a noise as it rolls across an idler. A wire brush will take off most of them. Use a razor knife to pick out what's left.

Not sure where it comes from. I just assumed it was from the A/C clutch.

Well Rick, You were right about the wait. The original code reared it's ugly head this morning on the way in to work. I was SURE the gas cap had corrected the code but you warned me. That's what I get for being an optimist.

Well Rick, You were right about the wait. The original code reared it's ugly head this morning on the way in to work. I was SURE the gas cap had corrected the code but you warned me. That's what I get for being an optimist.

Sorry Bro, If you haven't had any other work done like a fuel pump replacement, now is time to start looking for cracked and rotted hose.

Will do.

This cracked or rotted hose....Is there a chance that it is accessable exterior to the fuel tank?

Hope so. I am not equipped to drop one (fuel tank).

There is a vacuum diagram for an "older" Blazer with pictures in the Technical Section of the Blazer Forums.

Should I start looking here or do you think that by the nature of the code that if it is indeed a bad line that the probability is that it resides in the fuel tank?

Thnks-In-Advance,

Paul

Will do.

This cracked or rotted hose....Is there a chance that it is accessable exterior to the fuel tank?

Hope so. I am not equipped to drop one (fuel tank).

There is a vacuum diagram for an "older" Blazer with pictures in the Technical Section of the Blazer Forums.

Should I start looking here or do you think that by the nature of the code that if it is indeed a bad line that the probability is that it resides in the fuel tank?

Thnks-In-Advance,

Paul

As Old Master said, these are a bear to diagnose. The lines directly related to this issue will run the full length of the truck, from the engine to the tank. This small leak can be anything from the filler neck clamps, to vent hose, to the rubber filler neck that goes from the gas cap to the tank, to any of the other lines and hoses going into and out of the tank. Not to mention the fuel pump gaskets and tank vents.

The good thing is we have already eliminated the Gas cap, and it isn't snowing, which makes for a much nicer trip underneath.

Usually, nothing INSIDE THE TANK will throw this code.

The best thing is to tighten as many of the clamps and fittings that you can, and inspect for any obvious signs such as fuel leaking after fill up etc. Remember, this hole can be only .030 in diameter.

The Vacuum diagram might help, any vacuum leak needs to be fixed.

Got-Cha!

It's going up on jackstands Sunday afternoon for front brake rotor/pad replacement. I'll use four (4) stands instead of two and do an inspection of the vacuum lines up and down the rail. I'll post what I find.

Thanks for all of the help~!

Paul

FYI,,,The Problem was a hole in my fuel tank right on a seam. My mechanic told me that a hole on the seam cannot be fixed. He also informed me that the plastic nipples/fittings from fuel pump would probably break while dropping the tank so the fuel pump would have to be replaced.

The "Whine" that I thoght might be a water pump was (of all things) the water pump.

FYI,,,The Problem was a hole in my fuel tank right on a seam. My mechanic told me that a hole on the seam cannot be fixed. He also informed me that the plastic nipples/fittings from fuel pump would probably break while dropping the tank so the fuel pump would have to be replaced.

Seriously? Good grief....

I don't know about your pump, but mine has all metal fittings. And, if dropped properly, the fittings will not be damaged.