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Greg A
Greg A, Master Troubleshooter
Category: Buick
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Experience:  Working with Electronics & Cars for 25+ Years
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My 2001 Buick lesabre limited has fast flashing on the left

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My 2001 Buick lesabre limited has fast flashing on the left turn signal light. The front turn signal works, the back does not even though I've replaced the #3357 blubs repeatedly. What's wrong and how do I fix it. I tried to find a flasher, but nothing under the steering wheel that I can see.

Hello & Welcome,


Do you have a test light or multimeter you can use to do some testing?



Customer: replied 8 years ago.
Probably not. Not sure what a multimeter is.

Hi again,


That is a tool for measuring for voltage in an electrical system.


Let me ask you this: When you changed the bulb at the rear, did you notice any signs of damage or melting of the socket? Also, did you notice if there were any bent contact pins around the bulb?



Customer: replied 8 years ago.

Just change the bulb again today, and the bottom of the blub (which was still working and bright) did have a tiny bit of brown along the edge of the part that goes into the socket. No bent contact pins. PRobably is not relevant, but several of the #194 blubs were burned out. I keep a supply in my garage as I don't live close to the town where auto parts are sold.

I looked in the book that came with the car, and couldn't find anything that shows where to find the flasher unit (in case that is what is wrong). COuld that be it?


Hi again,


It is probably not the flasher, as it is doing what is supposed to do. The "Fast Flash" is actually a symptom or result of one or more of the lights in the circuit being out or not connected.


It would be nice to have a measurement device to be able to test and see if you are getting power back there, or to see if there is a loose wire somewhere. I will check the schematics for this vehicle and see if there are any fuses between the flasher unit and the tail lights, but I don't think there are any.


Thanks, XXXXX

Customer: replied 8 years ago.
All the lights work. Just the fast left turn signal on the dash, and when I get out of the car, the front light is flashing fast, the rear isn't flashing at all. BUt all the lights are working.

I believe you are referring to a light bulb that has two filaments in it, so if the flasher is not working at the back you may not notice it. This should be what the socket looks like and the signals coming in. Notice one is just for the parking light.




If you can, take a close look at the bulb in the socket and turn on the turn signal for the left side. Then do the same thing for the right side and compare the results. Do this with the parking lights switched on. If you can see a difference between the right and left sides, then that would say that there is a problem with wiring to that left side.


According to the label of the sockets, this light should also come on when using the brakes. Have you checked to see if that particular bulb comes on when the brake pedal is pressed. The left and right side should be doing the same thing when the brake is pressed.


Please let me know what you find.

Thanks, XXXXX

Customer: replied 8 years ago.

OK, just jumped in the car and drove down the road to a neighbor. He said that all the front signals work, but the left back brake light isn't coming on bright like the right side brake light. And of course, the back left turn signal wasn't working. But all the back lights are on (think theyare called daytime running lights, but not sure).

So the left side brake light isn't going bright when I pressed on the brake pedal.

Hi again - sorry for the delay.


I finally found the schematic for the rear lights. Below is the schematic for the left side.




I highlighted the flasher module and the connector that goes to the left rear light for the brake and turn signal. Without a test light to check if power is making it to that connector that I have highlighted (C400) or the bulb socket, about all you might be able to try would be the flasher unit itself. According to the manual, it is located behind the left side of the instrument panel, above the data link connector. Here is a diagram of the location.




I would look at Pin F on that module and make sure it is connected before replacing the module. I would also suggest getting a 12 volt test light or multimeter and testing before replacing any parts. You may be able to get either of these tools at a local hardware store.


Please let me know what you find or if you need more information.


Take Care Greg A.



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Here is what that C400 connector is supposed to be.