Question about 2003 Chevrolet Cavalier

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Check engine keeps coming on, i dont see anything wrong with engine, but i have a locked gas cap and the last time i put gas in and sealed it back up the next morning the check engine light was gone

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The fuel tank and lines is a pressurized system that is monitored by the computer and will set a emission code if there is a leak or you fill your tank with the vehicle running. 

Posted on Jul 18, 2009

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The number one customer easily resolvable issue is a loose gas cap. You must turn the gas cap until you hear 3 clicks. Another problem is a bad seal on the gas caps. I had a customer with a new locking gas cap and the problem was it wouldn't seal.

Posted on Jul 25, 2009


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Posted on Jan 02, 2017

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P1494 code

engine idle speeds, odd, hot? any real symptoms?

can be lots of things, the FSM covers it.
I think the ratio to real EVAP faILuers TO BAD CAP , IS LIKE 1000000:1 its so bad , new cars put , gas cap failure on dash !! display.
Give that fact, check cap first, and reset the ECU.
the EVAP system can be simple or hard.
Visual check the vacuum lines to all EVAP components
check all fuses.
then make sure gas cap is tight. (if cracked its no good) or a bad seal.
the reset the codes, using any scan tool. ($9 tool)
drive for a week see if it comes back, if comes back then its REAL.
if there is breach in the EVAP or bad VSV, (vacuum sol. valve)
then that takes the testing steps in the FSM.
or the EVAP system needs pressure testing, like they do
in all smog stations , at the cap.
if the leak down test fails, then you simply find that leak.
On can use any rubber tube held to the ear to hear a leak (after using a pressures source to the system.
if you have no tools, take it in. if DIY , buy them.
read the FSM. under this code, and the EVAP sections carefully.
there are 2 paths, it really is failing the EVAP or the OBD2 testing parts
are fibbing.
lots of guessing here, no tests...

the EVAP system , keeps gas fumes from polluting the air we breath.
it seals the tank vents and burns off all fumes as you drive.
that is what it does.
and is tested, all the time by the OBD2 system.
its very reliable in finding, any failure.
Your system fails the first step, it checks to see if the system
even holds pressure, and fails. the FSM explains how this
test is conducted, the steps and checks.

Cap issues?
my current jeep , the cap ratchet was dead. and would not get fully tight.
or the vacuum breaker inside is bad. (stuck open)
or the sealing ring is bad.
or someone put wrong cap on car.
or a locking cap that is wrong.
the cap holds pressure, and never a vacuum.
the vacuum breaker prevents fuel tank collapes (photos avail)

Dec 25, 2013 | 1999 Jeep Grand Cherokee

1 Answer

Why does service engine soon with gas cap code keep coming on even after buying new gas cap?

Get gas cap from dealer as some vehicles are having issues with the after market caps. What is the actual code and what's the vehicle year, make and model?

May 20, 2012 | Pontiac Grand Am Cars & Trucks

2 Answers

I changed my gas cap yesturday and my engine light went on today. would that have anything to do with it?

Hello: Yes if it is not designed for your truck it will cause the engine light to come. (the evap system) If you put a locking gas cap on that could be the problem. If you want a locking gas cap you will have to get a GM on

Aug 28, 2011 | 2007 Chevrolet Equinox LS New Cars

2 Answers

I'm getting gascap error and check engine light. What's causing the issue?

If you allready checked the gas cap and its on right.
Try replacing the gas cap with a new one.
You should here air wen you open the gas cap after driving
This is part of the emision controls and if it dosn't seal it will cause the check engine light to come on .

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2 Answers

Check Gas Cap alarm comes on and engine light is on

You gas cap is not on tight enough to seal causing the Check Engine Light to come on. When you tighten your gas cap you need to tighten it until it clicks at least 5 times, if it is tight than the seal on the gas cap may be bad. Replace with a OEM GM gas cap or a quality replacement that meets OEM specs.

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4 Answers

My check engine light came on and when i pushed my onstar button it said something about my gas cap. do you know what it may be? i did just put a locking one on my car

Your fuel system is a sealed system and part of the emission system also.If the gas cap is not tight or the seal has gone bad on the cap it will set a light.

Nov 10, 2009 | 2006 Saturn ION

1 Answer

06 chevy impala v6 3.9 liter engine. Check engine

there is a large evaporative leak. keep away form ottozoo, they dont have the brain power to actually diagnose a light bulb., their job is to sell parts., if they sell you the wrong parts tough.Take it to a qualified repair shop that does a lot of GM work or the dealer.

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3 Answers

Gas Cap Error with Check Engine light

By "Replace the gas cap", do you mean put it back on, or buy another one? If you fuel these trucks with the engine running, or don't tighten the gas cap, the light will come on. It will also come on when the seal in your gas cap goes bad. I have had to replace the gas cap on my jeep and dodge already. It fixed the problem both times.

Jul 07, 2009 | 2007 Dodge Ram 1500 Quad Cab Sport

2 Answers

Bought locking gas cap and now check engine light comes on.

well i dont think that would have anything to do with the gas cap and is a total coincidence. i would take the truck to advance auto parts or auto zone and have them scan the computer for codes

Dec 05, 2008 | 1995 Ford Bronco

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