P0303 Error Code - Cylinder 3 Misfire

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2004-2007 Cadillac CTS-V General Discussion Discussion, P0303 Error Code - Cylinder 3 Misfire in Cadillac CTS-V Series Forum - 2004 - 2007; So I took the V out for a drive today, and everything was running fine. I got onto the highway, ...
  1. #1
    vinnievis is offline Cadillac Owners Member
    Automobile(s): 2005 CTS-V
    Join Date
    Jan 2011
    Minneapolis MN

    P0303 Error Code - Cylinder 3 Misfire

    So I took the V out for a drive today, and everything was running fine. I got onto the highway, accelerated a bit to 70 on the entrance ramp, and no problems were apparent. 5 miles down the road I exited the highway, and drove through a parking lot. It seemed to be misfiring, but no check engine light. I could feel it surging/sputtering when trying to lightly accelerate, so I drove gingerly until I got onto my 30 MPH street. I accelerated with about 50-60% throttle through first gear and it was sputtering like mad. Finally the Check engine light came on and Flashed for a while and it was the P0303 - Cylinder 3 Misfire code.

    This just started randomly and I have never had this happen before.

    I have read a couple of threads and as soon as the car cools down a bit Im going to check the connections to the coil pack on 3 and to the Plug on 3. Hopefully that clears it up. If that doesnt clear it up, what is the next step? Swapping Coil Pack positions and plug wire positions?

    Also, Will I cause any damage to the engine with driving to help diagnose this? I dont want to cause any major damage trying to be a shade tree mechanic. Im assuming that I wont cause any permanent damage lightly driving, but scold me if I am wrong...

    BTW... Torque is an awesome app for the Droid in conjunction with the Bluetooth OBDII scanner!

  2. #2
    darkman's Avatar
    darkman is offline Cadillac Owners Master
    Automobile(s): 2005 CTS-V
    Join Date
    Nov 2005
    Spring, Texas

    Re: P0303 Error Code - Cylinder 3 Misfire

    If the published misfire diagnostic does not isolate the cause, perform the following suggestions as necessary:
    • Perform a fuel injector balance test for all 8 cylinders. If a fuel injector concern exists, it is possible to misfuel an entire bank of the engine, causing multiple cylinders on the same bank to misfire even though the root cause is a single fuel injector.
    • Inspect O2 sensor connections on the misfiring bank for corrosion or water intrusion. If water intrusion is found on the right bank, it may be due to the AC Evaporator Condensation dripping onto the O2 sensor harness. If this condition is found, reposition and shield the harness to prevent a repeat concern and repair the connections.
    • Check for excessive exhaust backpressure using the restricted exhaust diagnosis.
    • Swap the Position 1 O2 sensors side to side to see if the misfires move to the other bank of the engine. If so, replace the O2 sensor.

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