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PLEASE HELP !! DTC P0300 02 sonoma 4.3L

Discussion in 'GM Powertrain' started by BLOWOUT, Oct 5, 2012.


    BLOWOUT New Member

    Hello Everyone,
    I have a 2002 GMC Sonoma 4.3L VIN W. It has roughly 130,000 miles on it. Im getting DTC P0300 Random multiple cylinder misfire. I have done everything that I can think of. Here is a list of the things I have already replaced:
    - Plugs & Plug Wires
    - Distributor
    - Distributor Cap
    - Rotor Button
    - Ignition Control Module
    - Ignition Coil
    - Crank Shaft Position Sensor
    - Fuel Pressure Regulator
    - I also took the truck to a GMC dealership and they put a GM Tech 2 on it and tested the injectors and they checked out fine.
    - Also did a Fuel Pressure Test
    - Checked for vaccum leaks

    I am beyond stumped. The only thing I can think of that is left to replace could be the ECM/PCM. If anyone has seen or heard of this and has in info that they can pass along it would be very much appreciated. I forgot to mention the truck doesn't really misfire at idle only when driving. I hooked it up to a MAC OBD II scanner and monitored it. Every time its the same thing cylinders 1 & 4 are almost dead. Thanks so much for any help.
  2. PantheraUncia

    PantheraUncia Active Member 2 Years 1000 Posts

    This is a general guide:


    From looking around google, it could be an issue with a spark plug misfiring. I would check the plugs and cables (again). If you know someone with a diagnostic tool, see if they can find out which cylindar is mis firing.
  3. moogvo

    moogvo Epic Member 5+ Years 1000 Posts

    Are you losing coolant over time?

    BLOWOUT New Member

    My roommate has an OBD II scanner and its cylinders 1 & 4.

    - - - Updated - - -

    MOOGVO I really havent checked to see if im loosing coolant but i will check it and get back to you thanks

    BLOWOUT New Member

    My coolant levels appear to be fine.

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