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Chevrolet Repair/OBD2 emissions codes

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Question
I have a 2006 Chevy Avalanche 5.3l V8. I recently failed state emissions with codes p0300 & p0446. My vehicle has never run rough and two weeks ago I replaced the spark plugs & wires, had fuel injection service done and relaced the fuel cap and the "evac emissions control vent valve solenoid". I am a loss for what to do next. Please offer come suggestions.   Thank you.

Answer
HI STEVEN, WELL THIS IS A GOOD QUESTION BECAUSE IF YOU DO NOT HAVE A SCAN TOOL WE ARE ONLY GUESSING..WHAT YOU REALLY NEED TO DO IS GET A GM SCAN TOOL OR SIMILAR TOOL [GM SOFTWARE] TO RUN A FUNCTION TEST ON THE EVAP SYSTEM... TURNING THINGS ON AND OFF TO SEE WHAT IS OR IS NOT WORKING..THE PO 446 CODE IS FOR THE EVAP VENT VALVE SOLENOID SO THAT IS WHY YOU REPLACED THIS,BUT THERE ARE OTHER THINGS THAT CONTROL THIS SUCH AS A PURGE SOLENOID FOR ONE.. ALSO DID YOU MAKE SURE THE HOSE GOING TO THIS WAS CLEAN OF ANY DEBRIS ??? THESE VENT HOSES GET DIRTY AND WILL BLOCK THE FLOW TO THE VENT SOLENOID..SO YOU COULD CK THE HOSE GOING TO IT AND GM DOES HAVE A NEW UPDATED HOSE AND FILTER AND ROUTING TO THIS VALVE...IF ALL THIS LOOKS OK I WOULD URGE YOU TO TAKE THIS TO A SHOP THAT CAN RUN A DATA FLOW SCAN TO GET TO THE BOTTOM OF THIS..OR YOU WILL BE JUST THROWING PARTS AT THIS..
AS FAR AS THE PO300 THIS IS FOR A RANDOM MISFIRE CODE. WHICH BY THE SOUNDS OF THINGS YOU ALREADY KNEW THAT AS WELL. SO IF ALL SPARK PLUGS AND IGN WIRES ARE NEW,YOU ASK, WHAT ELSE IS LEFT.. IGNITION COILS ??? VALVE TRAIN ISSUES,SUCH AS BAD GUIDES...NOT VERY COMMON BUT WE HAVE SEEN THIS. DO YOU HAVE OVER 100K ON THIS ENG ??? IF YOU HAD A SCAN TOOL AGAIN YOU COULD CK FOR MISFIRE COUNTS AND ZERO IN ON WHICH CYLINDER OR CYLINDERS ARE CAUSING THIS SKIP..SO THIS MAYBE CHEAPER FOR YOU IN THE LONG RUN TO GET THIS SCANNED AT A GM SHOP THAT KNOWS HOW TO RUN THERE SCAN TOOL TO ZERO IN ON IT FOR YOU..THAT WAY IF YOU WANT TO INSTALL THE PARTS THIS WOULD SAVE YOU SOME CASH..AS FAR AS PASSING THE EMISSISON TEST,I WOULD FIX THE EVAP CIRCUIT PROBLEM FIRST AND THEN CLEAR THE MISFIRE CODE AND DRIVE IT FOR ABOUT 50 OR 60 MILES OR SO [ EASY ] NO BIG HILL CLIMBING] TO NOT SET THE MISFIRE CODE AGAIN AND GET IT INSPECTED. DRIVING IT FOR 50 MILES OR SO WILL GET THE MONITORS READY TO PASS INSP AND SHOULD NOT RESET THE CK ENG LIGHT..I WISH I COULD BE OF MORE HELP TO YOU BUT WITHOUT BEING THERE TO DO A HANDS ON SCAN IT IS KIND OF HARD. LET ME KNOW HOW THIS GOES AND GOOD LUCK TO YOU,,,TOM..

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TOM SHEETS

Expertise

PLEASE READ ALL OF THIS BEFORE ASKING ANY QUESTIONS. IF THIS CHEVY SECTION IS MAXED OUT.YOU CAN REACH ME IN THE OLDS/BUICK SECTION. Will answer questions from 6:00am to 10:00pm all days [EST][[[ NO DIESEL OR PAINT QUESTIONS]]] will answer all 1965 to present QUESTIONS ON ALL GM'S on mechanics of these cars. Keep in mind i am not there in person i am going on what you are telling me !! PLEASE IF ASKING A QUESTION GIVE ME AS MUCH INFO AS POSSIBLE. THE MORE THE BETTER. SUCH AS YEAR,MAKE,MODEL,ENGINE SIZE. THIS WILL HELP ME HELP YOU. I will not be able to answer all questions because of some situations that i would really need to be there and see things for myself,such as electrical issues. In many cases i would need wiring diagrams. I can also give you an estimate on what the cost would be at our repair shop as an idea to help you. Keep in mind that my answer is ONLY MY ADVICE,ck with your mechanic as well.. >> THANK YOU, TOM..

Experience

I have been a ASE certified master mechanic for over 30 years and certified IN ALL 8 CATEGORIES,[engine repair,engine performance,auto trans,manual trans,clutches,steering and suspension,brakes,electrical systems,heating and air/cond. I am also a state CERTIFIED inspector for over 30 years. I do computer work [pcm]fault codes,pcm flashing,state inspection monitor readiness,repairs on exhaust,fuel service,[injection and carburetor,] charging system problems, running issues,alignments,frame problems,tire balance,struts and of course standard and anti-lock brakes.

Organizations
nys state auto repair industry and ase group.

Publications
N/A

Education/Credentials
high school,4 years of tech school,and many many hours of auto training with many gm classes and aftermarket training classes..

Awards and Honors
ASE MASTER TECH CERTIFIED IN ALL 8 CATEGORIES.NYS INSP LICENSE AND A/C CERTIFIED

Past/Present Clients
MANY CUSTOMERS IN OUR BUSY SHOP.

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