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2002 Chevy Silverado 2500 Issues

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  • 2002 Chevy Silverado 2500 Issues

    Maybe some of you can help me narrow down what may be causing the following problems.

    First off let me mention I have replaced the coeslescent filter, fuel filter, spark plugs and wires, cleaned the o2 sensor and idle air control, and new air filter. The truck does not like to start on gasoline. I have to crank it for a while and multiple times for it to fire. When the weather is cold it will not idle on CNG. It stalls at every red light. On a side note what is the cng fuse labeled that will force it to switch over to gasoline?

    Thanks for any ideas,

  • #2
    Re: 2002 Chevy Silverado 2500 Issues

    Joe, I can't help you with the stalling problems, but the fuse is in the fusebox under the hood. When you are standing at the front of the truck it is on the right side. One of the fuses should be marked "CNG". On the newer GMs it is usually marked something like "AFS" (Alternative Fuel System?).


    • #3
      Re: 2002 Chevy Silverado 2500 Issues

      If you have changed to oxygen sensor and it didn't help, the next sensor to check is the ECT (engine coolant temperture) sensor. With a cold engine, check to see that it reads within 3 to 5 degrees of the IAT (intake air temperature) sensor. If that is OK, next check the MAP (manifold absolute pressure) sensor. If all checks out, make sure there are no intake manifold leaks or mechanical problems (compression) with the engine. Without showing any DTC codes one of the above things is most likely the problem. Both the AF ECU and the gasoline PCM share these sensors and the problems would be exibited on either fuel .