Headlights on, transmission jerks.

GOLGOSKY

MEMBER
1997 LEXUS ES 300
18,500 MILES

My Lexus ES300 generally runs well. However something strange happens ONLY when I turn on my headlights, the transmission jerks and shifts roughly. This is a recent problem. Also, my dashboard warning light indicated that my tail light is OUT, but I replaced it and all the tail lights seem to be working fine, so I've just ignored the dashboard light. The problem I'm asking about is the transmission. The transmission always works great, until I turn on the headlights. I don't understand what the headlights have to do with the transmission, but apparently they must be related. What do you recommend to solve this problem?

5 Replies

HMAC300

MECHANIC
48,601 POSTS

Have your battery and charging system checked. A battery in poor condition or low state of charge will cause driveability problems.

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Wednesday, February 29th, 2012 AT 8:43 PM

ROCKETMAN

MEMBER
7 POSTS

Had a van at work that would drop out of overdrive when the lights were turned on. I was not in charge of maintenance, but was puzzled what the relationship/cause was. It was a bad brake switch. The brake switch in that vehicle was mounted up on the brake pedal arm and was mechanical. It is in the circuit that kills the cruise control among other things (like maybe dropping to 3rd gear under constant braking). Your reported "problem" with the tail light seems to loosely support a similar scenario. The shop that identified the brake light switch still wanted to also replace the trans and I had to tell the clowns, try fixing the brake switch first and see if the problem persists (it fixed it, trans was fine). I don't know if they never made the connection between the transmission and the switch, they were fooled by some trans code or they were just service n'er do wells.

RocketmAAn
Mechanic wannabe.