1992 Lexus LS400 - Headlights/Shifting

[lewisautorepair]

I HAVE A 1992 LEXUS LS 400, WHEN YOU DRIVE WITHOUT HEADLIGHTS ON THE TRANS SHIFTS FINE. WHEN YOU TURN HEADLIGHTS OR PARKING LIGHTS ON AND DRIVE IT WONT SHIFT AND SHIFTS HARD WHEN IT DOES. THE R ON THE GEAR INDICATOR LIGHTS UP ALSO WHEN THE HEADLIGHTS ARE TURNED ON. ANY SUGGESTIONS?



FIXED!!!

[a&mauto]

I would be looking for a short between the two circuits in the direction of the tail lights and the reverse lights. Pull both bulbs out of both sides and see if the "R" still lights up.

[lewisautorepair]

how could this affect the shifting if it is in the tail light circuit and the light switch? just curious....

[liljoe]

I think I would be looking for a ground problem, sounds like the lights are back feeding through the shift indicator circuit and putting it in limp mode.

[steven kiser]

check the neutral switch. the tranny shifting hard indicates that the pressure is fine and the solenoids are being effected. as in all WEIRD issues i will discuss at length what happened to or was added to the car prior to the present issue. the time line won't be restricted to just prior i'll go back a way.

[lewisautorepair]

I SEARCHED THE TRUNK HARNESS AREA AND FOUND THE WIRING GOING UP THE TRUNK HINGES CUT BY THE HINGE AND GROUNDING OUT ON EACH OTHER. REPAIRED ABOUT 7 OR 8 CUT WIRES AND ALL IS GOOD. YAY!!!

[steven kiser]

thanks for posting. it appears that the rear parking lights were feeding current through the reverse light wire effecting the transmission voltage.