So, the LS400 is dead in the water currently. Came home and stopped quickly in front of my house. Ran in to get something, came back out and went to start the car. Dash lights come on and front defroster light blinking, but no interior lights, no headlights, no stereo, no power to the door locks or windows, no relays clicking, the climate control doesn’t work, the external climate temp isn’t reading, and when I turn the key, no crank no start. ECU already had capacitors replaced, passenger side harness tucked, thinking possibly relays? Drove it the day before to Big Bear and Back (About a 90 mile round trip) with no issues. Going to see if I somehow tore up the driver side harness, but that would only effect lights.

Tested the battery and alternator... Both are fine... So
now it’s checking fuses, relays, and grounds.

Update: It may be the immobilizer. I have power to the gauge cluster, seats, windows, but no power to mirrors, stereo, and the security light isn’t blinking. Also, my climate control comes on, but stays blank and the front defroster button is still blinking. Battery and alt tested fine.

Okay, so there is power to everything but the stereo, interior and exterior lights, and mirrors, and the car won’t start or crank. I’m at a loss right now. The security light isn’t blinking and the climate control still has a blank screen and the front defroster light is still blinking.

I took it to Autozone and they tested it. But someone pointed out to me if they tested it under load. I don’t think they did.

We’re going to check the harnesses and ECU next. The reason why is we checked all fuses. Main relay might be an issue. But when I tried to connect an OBDII just to test a theory, it kept giving an error code saying it couldn’t connect. That’s never happened before.

So we replaced the starter and starter relay. Still no start, no crank.

Finally found my login info again, so still nothing yet. After replacing the starter and starter relay and still not getting the car to even crank, I’m at a loss. I know when we put power to the starter relay, the car would crank and fire by turning the key, but as soon as power was cut, the car would die out. Also, the code reader will not communicate with the ECU still. Still have power to everything except the headlights/tail lights, turn signals, and stereo with the key in the on position. Turn the key to start and cluster goes dark and all dash lights shut off. Release
key and they come back on.