Question about 1998 GMC Sonoma

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My check engine light is on again. The code is a fuel system leak. I already changed my gas cap. Where do I look next?

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  • dslopsema Aug 09, 2009

    I believe it was a crack in the housing at the top of the fuel fill pipe. I put a piece of tape over it, and it seems to have helped. By the way, I also found out that to re-set the code, I had to disconnect the battery for at least a half hour because there is a capacitor to that keeps the computer running.



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Trace the EVAP lines and see if one is broken or disconnected.

Posted on Jul 28, 2009

  • Travis Mcilree
    Travis Mcilree Aug 09, 2009

    The fastest way to find the leak is to take it to a repair facility that has a "smoke machine" that they can hook into your evap system and trace the leak. It should only take a few minutes and is a lot easier than crawling all over the vehicle looking for leaks.

    I have seen problems like this where there are cracks that are very small and in places not easily seen, for example the top of a fuel tank is a possible place for a leak and it is not a very accessible place.


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And you cannot see any obvious signs of leaks? Is that the only code it shows?

Posted on Jul 28, 2009


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P0442 I got the check engine light in my GMC savana 2008 I get this code P0442 it said. a small leak in detected can someone please help me with this problem I reset the code 2 times already the first time...

The P0442 code is for a small leak in the pressurized emission system. It can be caused from something as simple as not tightening the fuel cap all of the way after fueling, or a leaky seal at the gas cap, or a leaky o-ring around a number of sensors and fittings in the emission system. If you are sure that you are tightening the fuel cap all of the way, and have already replaced the fuel cap and see no nicks on the seal on the fuel cap or fuel neck, you might need to have the vehicle hooked up to a smoke machine to try and find where the leak is coming from.

Oct 12, 2014 | Cars & Trucks

3 Answers

Runs good engine lt on code p0455

A loose gas cap or bad gas cap can cause this ,or filling gas tank while it running .or it could be a small leak in the evap system

Apr 21, 2014 | 2003 Jeep Wrangler

1 Answer

Check engine light/evap leak

Getting a smoke test is the right direction to go in.
The computer vents the gas tank to the vapor canister while the engine is running. It also pressure tests the system for leaks. Some where between the gas tank and the vapor canister there may be a leaking hose or valve. Or it could be the gasket on top of the tank where the pump assembly went in.
The gas cap could have been a source for the leak, the other things are not involved.

Apr 24, 2013 | Oldsmobile Cars & Trucks

2 Answers

Code po455 2004 chrysler sebring 2.4l sohc G vin code

The code is for a large leak in the fuel tank or evap system.

Some possible cause are - a leaking fuel tank, gas cap, hoses to and from the vapor canister and engine, and a faulty canister.
It's possible a valve is stuck open and allowing the engine to pull fumes in when the system is supposed to be closed, but if this were the case the computer should also set a code for that valve.

Here is the definition.

P0455 CHRYSLER Description The Evaporative emissions (EVAP) system is design to prevent the escape of fuel vapors from the fuel system. Leaks in the system, ca allow vapors to escape into the atmosphere. The leak detection system tests for EVAP system leaks and blockage.

During the self-diagnostics, the Powertrain Control Module (PCM) first checks the Leak Detection Pump (LDP) for electrical and mechanical faults. If the first checks pass, the PCM then uses the LDP to seal the vent valve and pump air into the system to pressurize it. If a leak is present, the PCM will continue pumping the LDP to replace the air that leaks out. The PCM determines the size of the leak based on how fast/long it must pump the LDP as it tries to maintain pressure in the system.
Read more:

Aug 21, 2012 | Chrysler Sebring Cars & Trucks

2 Answers

Check engine light came on went to auto zone said it was gas cap. Bought new gas cap. reset engine light. two days later check engine light is back on. what next?

Hi, if the code was P0455, there are other possible reasons. The computer fuel tank pressure sensor has detected a leak which could also be in the vapor canister, or the hose from the canister to the purge valve, or the purge valve itself may be leaking. Please inspect the system for these leaks. I may be able to provide some pics of these parts if you tell me your model, year, and engine info.

Evaporative Emission Control System Leak Detected (no purge flow or large leak)
What does that mean? This indicates a fuel vapor leak or lack of purge flow in the EVAP control system. It means a large leak has been detected. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.
Symptoms You likely won't notice any drivability problems.
Causes A code p0455 most likely means one or more of the following has happened:

  • A loose or improperly affixed gas cap
  • A non-conforming gas cap (i.e. not factory/original brand)
  • Other leak or damaged piece in EVAP system
Possible Solutions With a p0455, the most common repair is to:
  • Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back.
  • Otherwise, replace the gas cap, and/or
  • Inspect the EVAP system for cuts/holes in tubes/hoses (you may hear a vacuum noise or smell fuel), repair if necessary

May 14, 2011 | Chevrolet 2500 Cars & Trucks

3 Answers

My check engine light came on code P0446; dashboard says "check gas cap" i took it off retightened it and check engine light still on. I noticed that the metal flap for the gas nozzle is...

The metal flap should not trigger the sensor. Once you tighten the gas cap you should clear the code and see if it comes back. Otherwise it will take a while to go away.
If it does come back even though the gas cap is tight it could be the rubber seal around the gas cap replacing that can sometimes fix this issue also.

May 04, 2011 | 2008 Jeep Grand Cherokee

1 Answer


code P1456 set when there's small leak in the fuel tank system.
Most known reason for P1456:
-Didn't tight fuel cap on until it click for more that 3 time after fueling up and drove the car too long with cap loose.
-or a bad gas cap.
I'll try tighting the gas cap.
clear check engine.
if code come back, replace gas cap and clear check engine light again.

Dec 15, 2010 | 2001 Honda Odyssey

1 Answer

2006 Saturn Relay Check Engine Light

PO455 is a large evaporative fuel leak. A bad fuel cap is ONE of the things that COULD be the problem. Fuel system cleaning only lightened your wallet. Reading your post is confusing. Did all this start AFTER the Valvoline Wallet Flushing? If so , they left something loose or disconnected. I would find a qualified repair shop to fix the problem, and if it has anything to do with what Valvoline did, make them pay the bill.

Nov 12, 2009 | 2006 Saturn Relay

2 Answers

Check engine light keeps coming on replaced gas cap already

Your problem is in the evaporative emission system which is designed to prevent the escape of fuel vapors from the fuel system. Leaks in the system, even small ones, can allow fuel vapors to escape into the atmosphere. The light coming on can be caused by one of the following:

1. Defective or loose fuel cap
2. EVAP canister or hose cracked- not connected
3. Purge or vent solenoid defective
4. Vacuum leak at engine Government regulations require on-board testing to make sure that the evaporative (EVAP) system is functioning properly. The leak detection system tests for EVAP system leaks and blockage. It also performs self-diagnostics. You have tried the easy fix, the gas cap. Finding the leak now will require special equipment and testing procedures, might be better left to a professional.

Please let me know if this information is helpful. Positive feedback is appreciated. Thank You!

Mar 18, 2009 | 2003 Dodge Caravan

1 Answer

Check engine light on after overfill the tank. Check for codes at autozone, Change gas cap. Erase code. Ligth back on. Again to autozone. They say it is the gas cap. I let them know i have just replaced it...

You have a leak in the fuel system somewhere or a bad evaporative system sensor, the way the system works is the control module for the emission system pulls a vacuum on the gas tank and lines to check for leaks, if it can't get a certain vacuum level for a specified time it decides there is a leak and the check engine light comes on. This may be covered under the Federal Emissions warranty, call the dealer and inquire if the Evap System is covered.

Aug 27, 2008 | Hyundai Elantra Cars & Trucks

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