tranny does not shift at night with the lights on on 1993 Lexus LS400

why my transmission does not shift at night with the lights on?

Asked by for the 1993 Lexus LS400
2 answers
check the wiring harness in your trunk hinge. open it up and check for bare/crossed wires. this is really common and
causes voltage "feedback" when the lights are on.
It sounds like perhaps a ground is bad but all electrical connections would have to be looked at to see if when the lights or other electrical loads are on is there a voltage drop due to bad connections or grounds.