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.


How To Reach Alex
If you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, a master technician with the National Institute for Automotive Service Excellence. Send a letter to him in care of Truck Trend Garage, 831 S. Douglas Street, El Segundo, CA 90245, or e-mail us at trucktrend@sorc.com. Please include the VIN with your question. Due to the volume of questions received every month, we cannot guarantee that everyone's question will be personally answered or will appear in the magazine.

Can't wait for help with a problem you're having with your Truck or SUV? Ask the expert we trust here at Truck Trend Garage -- visit Alex Steele at www.RealWorldAutomotive.com.