I believe it is a black relay in fuse box try starting truck and see if you can feel the relay clicking when trying to crank.

Starter relay what it looks like

First make sure you have 12volts at battery when cranking it should not drop past approx 10volts check at battery and at cable at end of starter if good make sure you have good ground. if all checks out make sure truck is in neutral and emergency brake is on try to take jumper wire from positive of battery cable to small post of starter if truck starts you have a wiring problem.if not l would check starter there is a starter relay in fuse box but l have never had one go bad
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