LangleyD,
I just fixed mine, with a driver door switch.
In mine, here's what was 'not' working, along with the constant 'door ajar' lamp...
- Anytime the key was in the ignition, but not in 'run', you'd hear a constant chiming.
- When you started it, the interior dome and puddle lamps would remain on for 10min or so, unless you switched the interior lighting to 'off' (which killed the dash lighting also). Same thing for shutting it down and locking it. If the lighting wasn't turned 'off', you'd be staring at interior and puddle lamps 'on' until the battery saver turned them off - even if you locked it with the remote.
- Speaking of the remote, you could only program it if you had not been in the vehicle for 10min or so. Also, keep your foot off the brake pedal when cycling back and forth to put it in programming mode. This one was tricky.
- No retained accessory power (windows, radio)
- No door open chime (the soft single beep, vs the incessant chiming)
- If you have 'autolock' on, it doesn't work (this locks the doors after you start moving). I didn't even know the vehicle had this until I fixed the door ajar issue.
If those things sound familiar to you, you might want to try the door switch. It makes sense to do the driver's first - that door opens / closes much more than the others, on average. It took me about 45min to an hour to disassemble the thing, and I was using the service manual for the most part (which I'll say now, is poorly written / organized (but nicely illustrated)). About another 30min to put back together - but seeing the lamp off, and hearing silence - it's indescribable feeling - I was so happy to get that fixed.
As far as the other doors, if the driver's doesn't do it - if the previous owner had a small child, w/ car seat - it's likely they used the rear driver side door for that. Or, if they were a little older (but still relegated to the back seat), maybe they always entered from the same side as mom / dad. So maybe your test holds water. I'd try passenger front, rear hatch, and then the two rear doors last, as far as 'frequency of opening' (and likelihood of breakage). And all the WD40 / silicone lubricant in the world isn't going to fix it - all of my door latches were full of hardened white silicone (?) lubricant, from a previous owner trying to fix this.
The switches are local to the side of the car - so there are LH switches (driver side) and RH switches (pass side). They may be different by front / rear, but I'm not sure on that (I only had to buy one). Make sure you get the one(s) for the 4 door, not the sport, because they're not the same. I was given the wrong one to start with; the 'collar' surrounding the wiring pins was gray or green. The one for the 4dr had a pink sleeve / collar. When you compare the old vs. new - you see the 'plunger' (which is the part that controls the reporting of 'ajar' vs. 'closed') is slightly longer in the new one.
Now, if you've got different symptoms (you can find those here if you search) - pry the rubber wiring boot from the driver's door / body, and check inside to see if you have any breaks in the wiring - some have reported 1 to 3 black wires broken. If those are, that's most likely your issue. Since you don't have to remove the door panel to check on this (but I found it was easier to do so - and it's not hard at all to remove the door panel, once you do it once)

, you may want to check on this before doing anything else.
Good luck to you! I couldn't imagine living with this for 3 years or so...I'd have found the door chime module and ripped it out by now, I think