02 Envoy RS, vehicle fuses blowing

The crank fuse supplies the PCM with power and nothing else. The back up fuse supplies the park/neutral switch with power and then feeds back into the underhood fuse box to fuse 4 and 25. Ask your customer if he tows a trailer as those circuits are for the trailer harness. The problem may just be a defective neutral switch. I have seen other similar things on GM trucks where the circuits inside the neutral switch screw up the starter circuit. The switch may be causing a feedback problem and is drawing power backwards through a circuit and blowing the crank fuse. If nothing else, disconnect the remote starter and recheck all the main power wires to make sure nothing is shorted out. The dealer will always blame the aftermarket product because very few mechanics understand electrical and don't want to have to deal with anything that isn't factory installed. They take the easy way out. If you can solve the problem and show them their error maybe they will be less likely to blame others next time. sparky

Do those fuses in any way tie into the tail lights or brake lights? The mention about trailering plugs made me think of this..... There is a fairly well-known issue in Trailblazers where the circuit boards inside the taillamps go bad. But I am not sure which fuses blow when this happens. The problem is widespread enough that you can buy aftermarket circuit boards in the HELP! section at the auto-parts store. Maybe it is worth doing a little research into seeing which (if any) fuses blow when those circuit boards go bad.