Problem with the trunk lid of W140
 

Of late, my W140's trunk lid has delayed or even failed to pop out occasionally. It seems to me that the mechanism cannot sense the trunk being opened. Would anyone please tell me is there anything like a micro chip responsible for that function? If there is, where is it exactly and can I replace it myself?

Thanks in advance for any input!

ahh its the classic vacumm pump located somewhere in the trunk that is responsible for the trunk and the doors.

The trunk handle that pops out is controlled by the central locking pump located under the back seat on the right side. There is a micro switch on the trunk latch that sends a signal to the pump to operate. You could have a faulty micro switch, or a faulty element for the handle, or a faulty locking pump, or a wiring problem.

I had a problem with mine which worked intermitently, so using a Mityvac I checked the vacuum lines from the pump located under the rear seat [right side] and found a leak which I traced to the vacuum pod for the retractable trunk handle. I replaced the pod and that solved the problem.

Thanks for all the helpful replies! I would like to start the troubleshooting with the basic one. Would anyone please tell me where exactly the location of the micro switch is?