where is the crankshaft position sensor on a 2006 hummer h3

The crankshaft sensor is in the rear of the block near the starter here is a guide and a diagram below to show you the location.

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.

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hummer h3 2006 crankshaft senser replace twice back to back and still missing

That is because the crankshaft sensor will not cause misfire. Does this occur only at idle, or all the time and under load. A couple of common causes for misfire is water in the #1 spark plug port, a faulty ignition coil. If it counts misfires at idle that are barely noticeable, and diminish with increased engine speed, it could have valves leaking in the cylinder head. I believe there is a bulletin on this, and the water intrusion in the plug ports.