Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
What sort of diagnostic tools do you have? Scan tool? Multimeter?
Can you hear the fuel pump buzz when you first turn the key to the run position? It should buzz for about 3 seconds each time the key is turned to run.
It sounds like you have a short. I've seen a couple dozen of these trucks with rodent damage to the wiring under the under hood fuse box. Can you pull the battery box up and check the wiring underneath for signs of damage?
If it looks ok the next place to check will be SP205. It's the connector under the dash on the left of the steering wheel.
Splice pack SP205, is taped to the harness above the left side footwell light under the Instrument Panel (IP) on the left side near the back of the fuse block.Remove the "Comb". Connect a scanner to the DLC. Use a suitable jumper to short pin D, a Purple wire to the Dk Green wire at pin B. Attempt to communicate with the Powertrain Control Module (PCM).If communications work, use another jumper to short pins B and D to each of the other pins in SP205 one at a time. Determine which wire/module is causing the communications failure. When that wire/module is shorted to pins B and D, the scanner will go to "No Communications".Go to that module for a circuit failure in the Class 2 data circuit or power or ground issue going to that particular module.
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That's odd. The short must be closer to the battery junction box (underhood fuse box) then. Were you able to look underneath the box for rodent damage?