Left rear door is fully closed but dashboard indicates door ajar plus interior lines stay on

On my 2011 f150 I found crimped wires actually inside the door, about 6inches up the harness from where it goes in from the hinge side. Peal back the boot and remove the tape till you find it. Good luck.

i replaced the latch it didn't fix my problem

I had the same issue on my 2009 F150, so I watched a few videos on YouTube. In those videos, quite a few people tore the door apart which was useless unless you're replacing the entire harness. Just like a GuruB said, pull back the boot, carefully remove the tape and there you'll find snapped/exposed wires. The wires in my door were pretty bad so I used electrical tape and extra wiring to lengthen the wires in my harness until I buy a new one. This cleared the issue.

GuruB and JoeyTornado were right! I have a 2010 F-150 XLT supercab, and the rear left door ajar light was coming on the instrument panel. Tried the WD-40 fix - no help. Then I read these two posts. I pulled the wiring harness boot/grommet and wiggled around the taped wiring harness., Walla! Ajar light gone! I'll need to peel away the harness tape and find the culprit wire(s) for a permanent fix when I have time, but suffice it to say this is where the problem originated. Took all of 60 seconds to pull the grommet and check the harness! Thanks guys. Saved me a ton of expense and frustration with a dealer.