Have a 2003 LS170 with about 3000 hours. Consistently blowing the 5 amp fuse that feeds the EIC and seat/belt circuit. Everything seems fine until the ignition switch is turned to the 'start' position, when the fuse blows, get the alarm, etc. (But if we switch the service/run switch to service, engine starts and runs fine.) If we replace the 5 amp fuse in the engine compartment, prior to sitting in the seat, the EIC is dark.(normal operation) When you sit in the seat, it goes through its checks, all lights on for a few seconds and then they turn off, and the parking brake and seat belt lights flash. When you plug in the seat belt, both of these lights go out. Turn key to 'run', and you can hear the preheat solenoid pull in and times out for x number of seconds, after done with preheat, you hear the quick beep letting you know it's ready to start. At this time the hydraulic solenoid locks also work properly because I can move both foot pedals for hydraulics..... When you turn the key to 'start' is when the fuse blows after only a few seconds of the starter being pulled in. Alarm sounds, EIC is dark, etc. (But if we switch the service/run switch to 'service', engine starts and runs perfectly.) We have spent many, many hours going through all of the circuits / components. We have checked wire harnesses, jumpering out seat/belt switches, hydraulic lock solenoids, start interlock relays, swapped the start and preheat relays, fuel shut off, cleaned EIC board, etc. We even did some jumpering to isolate the two separate wires coming off the back of the 5 amp EIC fuse. Individually fused the R/LT GN wire that goes directly to pin 14 P2 on the EIC and individually fused the LT GN/R wire that feeds the seat belt switches then to the start interlock relay and to pin 4 P2 on EIC. The fuse that blows has 100% been on the wire that feeds the seat / belt circuit, not the direct wire to the EIC. A key thing we noticed was that this fuse only blows when engine is running or trying to start. It does NOT blow when replacing fuse and nobody is in seat, or when you sit in seat, or buckle seat belt. It ONLY blows when ignition switch is turned to 'start' or if engine is running and ignition switch is in run. This 5 amp EIC fuse is now consistently blowing when turning ignition key switch to 'start', but it wasn't always this consistent. About 2~ weeks ago was the first we started to see issues. One night, sat in seat and everything seemed normal until key was turned to 'start' and everything went dark, no attempt to turn engine over, and no alarm... got out of machine and came back after about 10 minutes. Sat in seat and everything seemed fine again, had lights on EIC but when key was turned to 'start' everything was dark again, no alarm, etc. Didn't look into the issue that night. The next morning dad stopped up to look at it, machine started right up perfectly, no issues for about a day or so, then we started to see the issue intermittently. might run for an hour or so, maybe minutes, or even seconds over the ~2 week period of troubleshooting. But now it seems consistent with what I wrote in the first paragraph. Anybody have any ideas? Are we missing anything? Or is it time to purchase the crazy expensive EIC board? The one area we didn't spend a lot of time physically jumpering out wires/circuits was on the ignition switch and service/run switch... I guess some contacts could be shorted in those switches, but hard to test because they have a molded plug where all wires come off/on at once and a lot going on inside them. Appreciate the help. Looking for any ideas, things to look at. Thanks!
