2003 Chevrolet Avalanche Won't start

  • 1 POST
  • 5.3L
  • RWD

Lost power while driving eventually stalled started it back up and got it home limping. Changed water pump because I knew it was going bad based on being able to hear it. Started right up and got 2 miles down the road and check engine light came on, then truck stopped and couldn't be restarted. Codes came back that I needed to replace 02 sensors and crankshaft position sensor, I replaced them and the truck still won't turn over. Any help?

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Friday, March 13th, 2015 AT 4:25 PM

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If the engine won't crank, that's a starter system problem, so that's what needs to be diagnosed. For the running problem, you may have made a very common mistake. Diagnostic fault codes never say to replace parts or that they're bad. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition.

When a part is referenced in a fault code, that part is actually the cause of that code about half of the time. Before replacing the part, which introduces more variables the computer might not be ready to learn, you have to check for wiring problems including stretched or corroded connector terminals, cut wires, wires rubbed through and grounding out, and things like that.

The front oxygen sensors' signals help the Engine Computer calculate the best fuel / air mixture, that's all. Except for very rare circumstances, they will not cause running problems and especially no-start conditions. For most of their failures you won't even notice it in engine performance issues.

The crankshaft position sensor is a different story. They often fail by becoming heat-sensitive, then they work again after they cool down for an hour. A lot of times they don't even have time to set a fault code so you're lucky you got that. The Check Engine light usually won't even turn on if that is the only fault code. There's well over 2,000 potential fault codes, and about half of them refer to things that could adversely affect emissions. Those are the only codes that will turn the light on.

Once you have the engine cranking, you'll need a scanner to view live data to see if the crankshaft position sensor is sending a signal to the Engine Computer. If it is not, there could be one of the wiring issues I mentioned, or there could be a mechanical problem to include the tone ring that interrupts the sensor's magnetic field or the spacing of the sensor from it.

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Friday, March 13th, 2015 AT 4:45 PM

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