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sprinkles08, ASE Certified Technician
Category: Chevy
Satisfied Customers: 22390
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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Check engine light on reading as large EVAP leak, had

Customer Question

Check engine light on reading as large EVAP leak, had solenoid on front of tank replaced last year at dealer, had some other part replaced two years ago (they had to drop the tank to access it) on top of fuel tank. Replaced fuel cap with new OEM cap from dealer, still an issue. This is frustrating as the vehicle runs fantastic, no issues whatsoever. could this be something simple like an PCV or EVAP control in the engine compartment. 2006 Silverado 5.3 Vortec w/ approx. 110,000 m. Like I said the truck runs fantastic.
JA: Does the light stay on, or does it blink?
Customer: Stays on constant, had a friend clear out the codes, twenty miles the light came back on constant.
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: Beyond the above actions nothing, prefer to resolve myself, but and constrained by time and extensive tools.
JA: Anything else you want the mechanic to know before I connect you?
Customer: No, If it is a problem that I an not able to handle I want to be prepared when taking it to a facility.
Submitted: 9 months ago.
Category: Chevy
Expert:  david craig replied 9 months ago.

Hi Im David.........the only thing you can do to track down this leak is a visual check of all of the evap lines and hoses. if you do not find a problem, then a smoke test has to be performed to see where the leak is. right now those are you only options instead of throwing parts at it.

Customer: replied 9 months ago.
Is there a progression of checks by likelihood of leak, such as MAP sensor, then PCV, etc?
Expert:  david craig replied 9 months ago.

the pcv is not part of the evap system nor is the map or maf...... the evap system is strictly for the absorption of fuel vapors and the venting of them. it starts in the engine compartment where the purge valve is located and run the entire length of the vehicle up to and including the gas tank and filler neck and charcoal canister.

Customer: replied 9 months ago.
Ty Gotcha, only fuel vapors. The purge valve on this vehicle is at rear of motor ?
Expert:  david craig replied 9 months ago.

Let me send you a pic......sorry for the delay. i own a shop and get quite busy

Expert:  david craig replied 9 months ago.

take the engine cover off and its right in front of you. it'll have a green test port cap near it

Expert:  david craig replied 9 months ago.

please dont forget to rate my service as its the only way i get credit for my help. thanks. i can still keep this open even after you rate me.

Expert:  david craig replied 9 months ago.

do you still need assistance?

Expert:  david craig replied 9 months ago.


Expert:  sprinkles08 replied 9 months ago.

Hello and welcome JustAnswer!

If it's setting a large leak code it could be a leaking line, canister, vent valve or purge solenoid, it could be the canister itself.

You'll want to visually inspect the whole system as well as the fuel cap's condition. If no problems an be found then a machine can be used to inject low pressure air and/or smoke to ensure the system actually does have a leak and help locate it.