Lexus Repair: Lexus electrical problem, factory bulbs, quality brand name


Question
Hello Leonard.
I have a year 2000 Lexus ES300.

When I turn on my headlights, my warning dash light comes on showing something wrong with the brake lights.

My brakelights work fine with the headlights off.

When I turn on the headlights, the right brakelight comes on and stays on, while the other 2 brake lights work normally (only when I brake).

Is this something I can fix?

Thank You
Dan

Answer
Dan,

The answer to your mystery lies most probably within the following two realms:

1) Have any of the rear taillight or brake light bulbs been replaced recently?  The reason I ask is that the taillight failure warning module that turns on the dash warning light is very sensitive to the quality of the bulbs.  There are many cheap Chinese and Taiwanese bulbs out there that cause problems such as you described.  If a bulb has been replaced recently (and you can recall which one was replaced) try replacing that bulb again with a high-quality, brand name bulb from your dealer or higher quality auto parts supply place (such as NAPA).  Make sure the replacement bulb looks EXACTLY like one of the original factory bulbs, as many wrong bulbs can look similar.)

To further help in your diagnosis, swap the affected bulb with the good bulb in the same position on the other side of the vehicle.  If the problem follows the bulb, the bulb is bad.  If the problem stays on the same side, the wiring harness in the vehicle is suspect.

2) If you haven't had any bulbs replaced recently, or if you are certain that the bulbs are all high-quality, I would wonder if the vehicle has sustained any flood or accident damage to the rear section of the vehicle, which may have damaged the wiring harness or the bulb socket.

If  the bulbs are of high quality, and there has been no accident damage, you should have the wiring inspected by your local dealer.  In this case, it's most likely a brake light wire shorted to the taillight wire.  

Wiring problems from the factory such as you describe are pretty rare (most of the time it's due to an outside influence such as flood damage or accident)  but possible.  Also, if it's not related to outside influence, and you have less than 50,000 miles on your vehicle, the wiring diagnosis and repair will be covered under warranty by your local dealer.

Hope that helps.

Leonard