1997 Lexus LX450, Viper 5806, Remote Start Won’t Work

Hi folks, I'm trying to get a Viper 5806V working in my LX450 and not having much luck. I'm pretty confident that it's a tach issue, but I've tried all the combinations I can think of and nothing seems to work. There is a factory alarm, which has been removed. There is no immobilizer. Unit is in automatic mode. I've tried virtual tach (no settings change, no wire connected to violet/white), voltage/off (electronics think it's on, but engine isn't on), and tach wire. For the tach wire, I've tried wiring to the tach wire on the speedometer, I've tried wiring to the blue/white cable on a fuel injector, and I've also tried the black/white cable on the ignition coil. In all tach wire cases, I've done the learn procedure (i.e. turn on the vehicle, press/hold the control center button within 5 seconds, the LED turns solid after 3 seconds, but still nothing. If I do virtual tach and remote start, it'll try to crank (for a long time) three separate times, but it doesn't actually turn on after the third crank. I've also reset the virtual tach several times and gotten confirmation from the system it's reset. Maybe it's not a tach issue? The activation input is connected to the parking brake wire for ground pulse. Neutral safety switch is grounded too. I'm pretty sure I just grounded the parking brake wire (and thus all three connections), but I'll double check that. System ground is the factory ground in the kickpanel. There is mention of a remote start shutoff switch, but my unit did not come with one and the port on the brain is molded plastic, no pins. Vehicle starts fine with key, door locks work perfectly, parking lights work perfectly, just no actual start after a solid crank. I'm at wits end here. This isn't my first rodeo, and I have a 5806V (with a remote start switch) in my 4Runner too. I'm thoroughly confused. Any thoughts? Best, wtcnbrwndo4u

I'd lean towards a tach issue as well assuming you have both ignition wires powered. You can count parking light flashes to be sure.