93 ls 400 battery swap, no lights, no shift. HELP Please.

[mysticmicheline]

1993 LS400 battery replaced, no lights and wont shift out of park

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OK, long story as short and sweet as I can make it.

Started off with a weird battery drain, jumping it off about once a week, then the battery was less than 10 volts, so i tried another battery, ( I might have accidentally reversed the polarity) it would only crank but not start so that didn't work, so I reconditioned and charged the original battery, put it in and it started right up....

problem is no lights ANYWHERE, all I have is horn and hazards. It also wont shift out of park.

I was advised to replace the 120 alt amp cartridge fuse. done. still no lights anywhere and I've called myself checking the other 3 fuses that it "could be", to no avail.

I'm in no position to "throw parts at it, and I'm at a loss, PLEASE HELP.

 

[isturbo]

This is almost certainly the security system locking out after the battery was disconnected. The LS400 of that era has a factory immobilizer that can go into lockout mode when power is lost, especially if the battery was fully dead before replacement.

First thing to try: lock and unlock the car with the key fob, or manually with the key in the door. On some of these the security system resets with a proper lock/unlock cycle after power is restored.

If that doesn't work: sit in the car with the door closed, insert the key, and leave it in the on position without cranking for about 30 seconds before you try to start. Some variants of the factory security system have a timeout reset.

If you're still stuck after both of those, the next step is checking whether the ECU has thrown any codes -- even with no-start symptoms the OBDII port should still be live if the battery connection is good. A code 78 or anything in the security/immobilizer range confirms the lockout theory.

Let us know what happens with the fob reset first.