Start by using a test light or voltmeter to test the battery's voltage. Normally we would start right on the battery posts, not the cable clamps, but GM makes that impossible with their side-post batteries.
You should have a smaller positive wire leaving the battery. Follow that one to the next accessible test point and put one test light probe there. It should still light up. Now move the other probe from the negative battery post to where the smaller wire bolts to the body, and test there. You're looking for the first place you don't have voltage. That will be the point of the bad connection.
For the positive part of the circuit, you may have to follow the larger cable down to the starter. GM likes to use that terminal as a common tie point for the circuits that feed the truck. If you have voltage there, we'll have to check on the individual circuits.
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Tuesday, January 8th, 2013 AT 2:10 AM