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Thread: code p0420

  1. #1
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    Default code p0420

    hay out there well i have 03 5.3 silverodo with 187000 miles it had to happen sooner or later. it started 2 sputter and shut off it will start but wont stay running. the codes that show up are p0171 p0174 p0420 . any help out there. thanks takein the high road

  2. #2

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    Quote Originally Posted by luvit4it View Post
    hay out there well i have 03 5.3 silverodo with 187000 miles it had to happen sooner or later. it started 2 sputter and shut off it will start but wont stay running. the codes that show up are p0171 p0174 p0420 . any help out there. thanks takein the high road
    Here is some Information that should help with the Trouble codes you have,

    For Both Trouble Code.......P0171 and P0174 may mean that one or more of the following has happened:


    • The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
    • There could be a vacuum leak downstream of the MAF sensor.


    Possible Solutions:

    • In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
    • Inspect all vacuum and PCV hoses, replace if necessary
    • Check for a dirty fuel filter and proper fuel pressure




    A Trouble Code.....P0420 may mean that one or more of the following has happened:


    • Leaded fuel was used where unleaded was called for
    • An oxygen sensor is not reading (functioning) properly
    • The engine coolant temperature sensor is not working properly
    • Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
    • Retarded spark timing
    • The oxygen sensors in front and behind the converter are reporting too similar of readings

    Possible Solutions

    Some suggested steps for troubleshooting a P0420 error code include:

    • Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
    • Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
    • Inspect the downstream heated oxygen sensor (HO2), replace if necessary
    • Replace the catalytic converter
    Last edited by 99'HEARTBEAT; 11-04-2011 at 06:22 PM. Reason: Added Infor.

    MIKE


    99"SILVERADO
    5.3 l 3.73 l G80
    BLACK BEAR CUSTOM TUNE
    SNUGTOP l COLORMATCH l KATZKIN










  3. #3
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    Cool

    thanks 4 the help.i have fond my fuel psi is not to spec i'am going 2 change the filter i'am told 2 check the inlet strainer but i dont know where it is if anyone could help i would be thankful happy truckin takin the high road

  4. #4
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    Default

    I could be wrong on this but I believe the inlet strainer is actually inside the fuel tank, I know on my 90 Lumina it has a "sock" or strainer on the actual sending unit inside the tank to block contaminents from entering the fuel lines. It is a replaceable $10.00 item, but the labor involved is priceless...

  5. #5
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    thanks alot i figured that where it might be i'am so looking forward to this!thanks again 4 the help

  6. #6

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    P0171 and P0174 mean that both banks are too lean. They are not MAF codes.

    What is your fuel pressure? Sounds like it's time for a new pump.

    P0420 is a non functioning cat. Get the truck running first, then deal with this code.
    Last edited by 2COR517; 11-06-2011 at 07:34 AM.
    When you hear hoofbeats, look for horses not zebras.

  7. #7

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    Quote Originally Posted by 2COR517 View Post
    P0171 and P0174 mean that both banks are too lean. They are not MAF codes.

    What is your fuel pressure? Sounds like it's time for a new pump.

    P0420 is a non functioning cat. Get the truck running first, then deal with this code.
    Correct.....I missed that.....the problem with both 171 and 174........means that both 02 sensor's are too lean.
    Last edited by 99'HEARTBEAT; 11-06-2011 at 10:42 AM.

  8. #8
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    fuel pressure is 15 psi i drop the tank and clean all the lines and still get 15 psi anything esle 2 check before i get a new fuel pump. thanks for all your help

  9. #9

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    Time for a fuel pump

  10. #10
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    Cool thanks

    thanks to u all for your help.it was the fuel pump all codes have cleared them selfs. again thanks

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