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ToyotaTom
ToyotaTom, Toyota Technician
Category: Toyota
Satisfied Customers: 1401
Experience:  Toyota, ASE, MSE, MECP Certified
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Check engine light comes on my toyota tacoma 2002 4 cyl. Computer

Resolved Question:

Check engine light comes on my toyota tacoma 2002 4 cyl. Computer reads vacuum leak in gas tank or lines. How can I fix?
Submitted: 3 years ago.
Category: Toyota
Expert:  ToyotaTom replied 3 years ago.

ToyotaTom :

Hello, and thank you for choosing Just Answer to help you with your questions!

ToyotaTom :

Did they say exactly what the code in the computer was? It should read something like P0446 or something of the sort. Will need the code in the computer to start to try and diagnose.

ToyotaTom :

These codes can come up for a hundred different reasons. There are a couple vacuum valves that are prone to failure resulting in a check engine light. Also it could come on just because the fuel cap was left loose the last time you filled up the tank.

ToyotaTom :

Without a handful of tools you probably don't own, self diagnosis would be nearly impossible.

ToyotaTom :

You could try the simple things. First remove your gas cap. You'll see a rubber o ring inside the cap at the base of all the threads where it screws in. Take a bit of vaseline and grease up this o ring a little bit and put the gas cap back in. Also, do a quick visual inspection under the hood and make sure there are no vacuum lines that are disconnected, especially around the area of your air box (air filter)

ToyotaTom :

If all looks good, everything is connected and you lubed up the gas cap and the light comes back on, chances are usually one of your vacuum switching valves have failed. The part is about 60 bucks, and you'll usually end up paying about an hour labor for the repair, including diagnosis.

ToyotaTom :

I would have to recommend the dealership for this, since the dealership techs are trained and familar with this type of evaporative emission system

ToyotaTom :

If there is anything else I can help you with, please let me know.

Customer :

I will get a new reading on the code. have a new gas cap, parts place checked under the hood and found nothing unusual -loose or cracked rubber -the code does point to evap. emission system.

ToyotaTom :

I'll explain it simple readers digest format...

ToyotaTom :

The evaporative emission system, basically puts the entire fuel system in as a sealed system. Kind of like your cooling sytem (if it wasn't sealed, you'd be leaking coolant)

ToyotaTom :

It does this for the fuel vapors for emissions. Every now and then, it will pull the entire system down into a vacuum, and do self-tests to make sure it is still completely sealed

ToyotaTom :

Even a tiny pin hole leak in one of the rubber hoses will cause a check engine light

ToyotaTom :

If the gas cap is tight, and there aren't any obviously disconnected vacuum lines, then you will need some tools to figure out exactly what has failed. A hand vacuum pump, something to actuate the vacuum switching valves, etc will be necessary.

ToyotaTom :

Many times you'll find that the VSV's will leak slightly, (not hold the vacuum like they're supposed to) and then it will trigger a light

Customer :

I understand the basics. I reset the light, then it will bun 2-3 tanks of gas and come on again while I am driving on flat level ground at about 45-50 mph.

ToyotaTom :

On yours, it is a key-on style test. IT has to run through a VERY specific drive cycle for it to run through that test. Some people never really complete that cycle

ToyotaTom :

And the check engine light won't come on until it sees that drive cycle fail twice in a row

Customer :

Will get you some more info. tomorrow. I will replace all components one at a time until I fix it. I would like to start with the one that gives the most problem. Thanks, Paul

ToyotaTom :

I'll be happy to help you with the specific codes that are being given. However, it's really not necessary to just start throwing parts at the truck until it finally gets fixed

ToyotaTom :

I would have to recommend find out exactly what is causing the problem, replace a part and fix it right the first time. Once you get me the code that's stored, I'll try and help you to test it so we know we're going after the right part. Have a good night :)

Customer :

Good deal. Will get the code asap. Paul

ToyotaTom :

Just checking up on you to see if you had the code pulled yet or not

Customer :

Light came on yesterday and I got a reading today.

Customer :

PO 441

Customer :

Evaporative Emission System Incorrect purge flow.

Customer :

Does any of this help narrow down the part I need?

Expert:  Toyotapro replied 3 years ago.

Before this became an issue was any work done to the truck?

Have you done a visual to be sure none of the vaccum lines are pulled loose from the canister under the truck or under the hood for the evap system?

Expert:  ToyotaTom replied 3 years ago.

This could be anything from a kinked hose, disconnected hose, to a restriction in the hose, canister, or valve, or the valve itself failing. If nothing was touched then chances are the VSV itself has failed, and either isn't opening correctly or is leaking. However anything at this point will need to be checked by the dealer. The valve is about $60 if that is what failed. It could be a charcoal canister, or about 20 other things. There is a sequence of tests that need to be performed to find out exactly what failed. You could probably fix it yourself by throwing a dozen different parts at it and spending hundreds of dollars until something works, But I would say that it would be worth the $50 diagnostic fee to determine the correct cause of, and solution to your problem.

 

Off hand I would say that it's likely the purge VSV has failed, however rather than throwing random parts at it you really should have it checked out by someone with all of the proper tools and equipment to verify.

ToyotaTom, Toyota Technician
Category: Toyota
Satisfied Customers: 1401
Experience: Toyota, ASE, MSE, MECP Certified
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