Question: The RAP relay is clicking like a turn signal flasher on my 2002 GMC Yukon XL with 328,678 miles. It starts and stops, and it happens when the turn signals are off.
Answer: That's serious mileage. RAP stands for Retained Accessory Power. The RAP relay keeps voltage applied to the sunroof, power windows, door locks, radio(s), and OnStar with the ignition off and all doors closed. It is managed by the body control module and will deactivate when a door is opened, reaches its 20-minute time limit, or battery voltage decreases below a prescribed amount. You really need a professional to efficiently diagnose a problem like this. With the aid of the proper scan tool, data such as door switch operation, battery voltage, and ignition input can be quickly viewed. The problem can range from a misadjusted door to an expensive body control module. My only DIY suggestions would be checking the battery and charging system, trying a known-good relay, and pushing and pulling on each door (including the liftgate) while the relay is clicking. This could lead you to a bad door-jamb switch, or out-of-line door.
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