Question about 2004 Chevrolet Silverado

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I have a 2004 Chevrolet Surburban...... It was cutting out real bad, when we cleared the code on it, it ran good. It has a 5.3L engine, It is throwing the code: P0340.... Catalyst System Effenicy Below Theshold Bank 2

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  • toby78611 Jun 03, 2010

    I said it was cutting out, it is losing all power now...... You will be driving it and it will start to lose piwer. You can hold the gas pedal all the way to the floor and get no response.......

  • toby78611 Jun 03, 2010

    It it losing all power while you are driving it. While driving down the road, it will start to bog down and you can push the gas pedal to the floor and it wont pick up speed, till its ready......

  • toby78611 Jun 04, 2010

    Thanks for the help. It was a bad cat...... I revved it up and all kinds of that honeycomb stuff blew out.

  • toby78611 Jun 04, 2010

    Thanks for the help. It was a bad cat...... I revved it up and all kinds of that honeycomb stuff blew out.

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  • Master
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I P0340 means that the rear cat is either switching too fast or not at all

more often then not this is a result of an exhaust leak or a bad O2

However, in your case, with the vehicle running real bad I am going to assume that your cat is bad

to confirm, simply disconnect your exhaust after the front o2's and retest

if your truck runs great then its time for a new cat


Let me know if you need any further help and/or assistance discarding the bad cat
Sean

Posted on Jun 03, 2010

  • Sean Reisdorf
    Sean Reisdorf Jun 04, 2010

    Excellent job

    Glad I could help

    Sean



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  • Master
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PO340 indicates a problem was detected in the camshaft position sensor circuit. Since it says circuit, that means the problem could lie in any part of the circuit. The sensor itself, the wiring, or even in the PCM. A code PO340 could mean one or more of the following.

  1. A wire or connector is grounded/shorted/broken/corroded
  2. The camshaft Position Sensor has failed
  3. The PCM has failed
  4. There is an open circuit
  5. The crankshaft position sensor has failed
Diagnosis can be tricky with this code. Here are some things to try.
  1. Visually inspect all the wiring and connections
  2. Check for continuity in the circuit wiring
  3. Check the operation (voltage) of the camshaft Position Sensor
  4. Replace the Camshaft Position Sensor as required
  5. Also check the Crankshaft Position Sensor
  6. Replace any damaged connectors or wiring
  7. Have the PCM checked and replace if necessary.

Posted on Jun 02, 2010

  • NOT ME Jun 03, 2010

    GM Code PO340 is not Catalyst System Efficiency. Code PO340 is Camshaft Position Sensor Circuit Malfunction. I have described in detail how to troubleshoot this problem. This sensor will cause exactly what you are experiencing. More than likely replacing the camshaft position sensor will solve the problem but like I said it can also be the crankshaft position sensor or wiring.

  • NOT ME Jun 04, 2010

    Odd you were getting a code PO340 with a bad cat. You should have been getting code PO430. Weird! But you solved your problem which is a good thing. Have a great day.

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