The liftgate in my suburban will disengage, but I am unable to open it. While riding all the door locks will constantly lock and unlock. The only way I can open the rear of the vehicle is by pulling the white cord found inside the door panel (we let it hang out). When the lock on the liftgate disengages I have to get out and push the door to shut/lock it, otherwise I keep getting message access gate is open. We have replaced the entire lock on the liftgate and we still have problems.

 

I had a similar issue. My 07 Suburban had a chronic issue of displaying on the DIC " Rear Access Open ". The lift gate would open sometimes and sometimes not. When the " Rear Access Open " message appeared the chimes would ring three times and the interior courtesy lights would come on. Sometimes these would happen constantly, drove me crazy!!! I took off the back lift gate panel and checked all the wires and such the best I could. I found nothing that appeared to be an issue. After a week of this I finally took to the dealership. The charge is around $276.00 and they told me there was a purple wire up in the headliner area by the rear lift gate that was intermittently shorting to ground. Going to pick up truck later today. I guess only time will til if it's really fixed or not.

 

Power locks cycling indicates a voltage drop. The poster above is on the right track about a shorting wire. Something is causing the voltage drop, and I'd say it has nothing to do with your tailgate. That's probably just a symptom of another issue.

First thing I would do is check the battery cables. I'd bet a dollar that one of the cables is loose, and occasionally breaking contact on bumps and vibrations as you drive. If that's not the case, then check ground wires under the hood to see if any are frayed or loose.