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Toyota Avalon - All lights blink/flash/strobe

We have had this car since new in 2000. It has been a great car and still could be except for this one problem it developed a year ago. It has 180,000 miles on it. What is happening is that the lights blink/flashing/strobe what ever you want to call it. We have made repeated trips to the (same) mechanic (garage) to repair the problem. You would think they would figure it out after the third trip. However they keep going to the battery, battery cables, and the alternator. This last trip they replaced all with a new battery, battery cables, and alternator. Still the problem persists, blinking/flashing/strobing lights and oh yes a much reduced gas mileage. The Toyota mechanics have no clue where to go now to diagnose and fix. Has anyone out there have or had the same problem and may know the fix?

Are you talking about the headlights and tail lights? Or the dashboard lights?

In any event, when all the lights on a circuit blink, my first suspect would be a defective circuit breaker or a short in the wiring somewhere on that circuit. Provided the battery and alternator voltage measure ok, and the associated connectors have been cleaned and tightened, those wouldn’t be a first suspect.

A fuse or bad connection at the fuse holder – while less likely – could cause this problem too. If that circuit’s fuse has a small crack, it could work and pass current until it heated up from the current flowing through the higher than normal resistance, then the heat would could open and cut off the current flow, which would cool it off, and then whole thing would repeat, resulting in the lights turning off, then on, etc.

I’m sort of surprised this is taking multiple trips to the shop. You may need to find a different shop who has someone there with specific Toyota electrical training and experience. When you find the right person, they’ll be able to quickly locate the problem with the aid of the schematics.

The problem might be with the body Electronic Control Unit.

The body ECU takes voltage directly fom the charging system, regulates that voltage and distributes it to all the lights in the vehicle.


If it is an ECU fault, then my comment about why it is taking so many trips wouldn’t apply. Debugging the ECU could be time consuming and difficult to pin down the problem. If that’s the case, the OP should definitely seek out Toyota experienced help. This may require a dealership shop. Good informative post @Tester.