The bulb failure light system works on voltage differential between the left and right bulbs, whether it's the taillights, brake lights, etc.

If a bulb is burned out, then it senses a difference in current going to each side, then turns on the light.

You need to make sure the bulbs are the correct bulb for the application, and make sure they are the same brand on both sides.

The electrical terminals on these taillight assemblies had some issues. I worked on these when they were still under warranty and we ended up replacing all the terminals with a newer style terminal that had more tension and solved the connection problems.

Use only good quality bulbs.

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